## Comparison Operators

Comparison operators, as their name implies, allow you to compare two values. You may also be interested in viewing the type comparison tables, as they show examples of various type related comparisons.

Comparison Operators
Example Name Result
\$a == \$b Equal true if \$a is equal to \$b after type juggling.
\$a === \$b Identical true if \$a is equal to \$b, and they are of the same type.
\$a != \$b Not equal true if \$a is not equal to \$b after type juggling.
\$a <> \$b Not equal true if \$a is not equal to \$b after type juggling.
\$a !== \$b Not identical true if \$a is not equal to \$b, or they are not of the same type.
\$a < \$b Less than true if \$a is strictly less than \$b.
\$a > \$b Greater than true if \$a is strictly greater than \$b.
\$a <= \$b Less than or equal to true if \$a is less than or equal to \$b.
\$a >= \$b Greater than or equal to true if \$a is greater than or equal to \$b.
\$a <=> \$b Spaceship An int less than, equal to, or greater than zero when \$a is less than, equal to, or greater than \$b, respectively.

If both operands are numeric strings, or one operand is a number and the other one is a numeric string, then the comparison is done numerically. These rules also apply to the switch statement. The type conversion does not take place when the comparison is === or !== as this involves comparing the type as well as the value.

Warning

Prior to PHP 8.0.0, if a string is compared to a number or a numeric string then the string was converted to a number before performing the comparison. This can lead to surprising results as can be seen with the following example:

<?php
var_dump
(== "a"); // 0 == 0 -> true
var_dump("1" == "01"); // 1 == 1 -> true
var_dump("10" == "1e1"); // 10 == 10 -> true
var_dump(100 == "1e2"); // 100 == 100 -> true

switch ("a") {
case
0:
echo
"0";
break;
case
"a"// never reached because "a" is already matched with 0

echo "a";
break;
}
?>

<?php
// Integers
echo <=> 1// 0
echo <=> 2// -1
echo <=> 1// 1

// Floats
echo 1.5 <=> 1.5// 0
echo 1.5 <=> 2.5// -1
echo 2.5 <=> 1.5// 1

// Strings
echo "a" <=> "a"// 0
echo "a" <=> "b"// -1
echo "b" <=> "a"// 1

echo "a" <=> "aa"// -1
echo "zz" <=> "aa"// 1

// Arrays
echo [] <=> []; // 0
echo [123] <=> [123]; // 0
echo [123] <=> []; // 1
echo [123] <=> [121]; // 1
echo [123] <=> [124]; // -1

// Objects
\$a = (object) ["a" => "b"];
\$b = (object) ["a" => "b"];
echo
\$a <=> \$b// 0

\$a = (object) ["a" => "b"];
\$b = (object) ["a" => "c"];
echo
\$a <=> \$b// -1

\$a = (object) ["a" => "c"];
\$b = (object) ["a" => "b"];
echo
\$a <=> \$b// 1

// not only values are compared; keys must match
\$a = (object) ["a" => "b"];
\$b = (object) ["b" => "b"];
echo
\$a <=> \$b// 1

?>

For various types, comparison is done according to the following table (in order).

Comparison with Various Types
Type of Operand 1 Type of Operand 2 Result
null or string string Convert null to "", numerical or lexical comparison
bool or null anything Convert both sides to bool, false < true
object object Built-in classes can define its own comparison, different classes are uncomparable, same class see Object Comparison
string, resource, int or float string, resource, int or float Translate strings and resources to numbers, usual math
array array Array with fewer members is smaller, if key from operand 1 is not found in operand 2 then arrays are uncomparable, otherwise - compare value by value (see following example)
object anything object is always greater
array anything array is always greater

Example #1 Boolean/null comparison

<?php
// Bool and null are compared as bool always
var_dump(== TRUE);  // TRUE - same as (bool)1 == TRUE
var_dump(== FALSE); // TRUE - same as (bool)0 == FALSE
var_dump(100 TRUE); // FALSE - same as (bool)100 < TRUE
var_dump(-10 FALSE);// FALSE - same as (bool)-10 < FALSE
var_dump(min(-100, -10NULL10100)); // NULL - (bool)NULL < (bool)-100 is FALSE < TRUE
?>

Example #2 Transcription of standard array comparison

<?php
// Arrays are compared like this with standard comparison operators
function standard_array_compare(\$op1\$op2)
{
if (
count(\$op1) < count(\$op2)) {
return -
1// \$op1 < \$op2

} elseif (count(\$op1) > count(\$op2)) {
return
1// \$op1 > \$op2

}
foreach (
\$op1 as \$key => \$val) {
if (!
array_key_exists(\$key\$op2)) {
return
null// uncomparable

} elseif (\$val \$op2[\$key]) {
return -
1;
} elseif (
\$val \$op2[\$key]) {
return
1;
}
}
return
0// \$op1 == \$op2
}
?>

Warning

# Comparison of floating point numbers

Because of the way floats are represented internally, you should not test two floats for equality.

### Ternary Operator

Another conditional operator is the "?:" (or ternary) operator.

Example #3 Assigning a default value

<?php
// Example usage for: Ternary Operator
\$action = (empty(\$_POST['action'])) ? 'default' \$_POST['action'];

// The above is identical to this if/else statement
if (empty(\$_POST['action'])) {

\$action 'default';
} else {

\$action \$_POST['action'];
}

?>
The expression (expr1) ? (expr2) : (expr3) evaluates to expr2 if expr1 evaluates to true, and expr3 if expr1 evaluates to false.

It is possible to leave out the middle part of the ternary operator. Expression expr1 ?: expr3 returns expr1 if expr1 evaluates to true, and expr3 otherwise.

Note: Please note that the ternary operator is an expression, and that it doesn't evaluate to a variable, but to the result of an expression. This is important to know if you want to return a variable by reference. The statement return \$var == 42 ? \$a : \$b; in a return-by-reference function will therefore not work and a warning is issued.

Note:

It is recommended to avoid "stacking" ternary expressions. PHP's behaviour when using more than one unparenthesized ternary operator within a single expression is non-obvious compared to other languages. Indeed prior to PHP 8.0.0, ternary expressions were evaluated left-associative, instead of right-associative like most other programming languages. Relying on left-associativity is deprecated as of PHP 7.4.0. As of PHP 8.0.0, the ternary operator is non-associative.

Example #4 Non-obvious Ternary Behaviour

<?php
// on first glance, the following appears to output 'true'
echo (true 'true' false 't' 'f');

// however, the actual output of the above is 't' prior to PHP 8.0.0
// this is because ternary expressions are left-associative

// the following is a more obvious version of the same code as above
echo ((true 'true' false) ? 't' 'f');

// here, one can see that the first expression is evaluated to 'true', which
// in turn evaluates to (bool)true, thus returning the true branch of the
// second ternary expression.
?>

### Null Coalescing Operator

Further exists the "??" (or null coalescing) operator.

Example #5 Assigning a default value

<?php
// Example usage for: Null Coalesce Operator
\$action \$_POST['action'] ?? 'default';

// The above is identical to this if/else statement
if (isset(\$_POST['action'])) {

\$action \$_POST['action'];
} else {

\$action 'default';
}

?>
The expression (expr1) ?? (expr2) evaluates to expr2 if expr1 is null, and expr1 otherwise.

In particular, this operator does not emit a notice or warning if the left-hand side value does not exist, just like isset(). This is especially useful on array keys.

Note: Please note that the null coalescing operator is an expression, and that it doesn't evaluate to a variable, but to the result of an expression. This is important to know if you want to return a variable by reference. The statement return \$foo ?? \$bar; in a return-by-reference function will therefore not work and a warning is issued.

Note:

Please note that the null coalescing operator allows for simple nesting:

Example #6 Nesting null coalescing operator

<?php

\$foo
null;
\$bar null;
\$baz 1;
\$qux 2;

echo
\$foo ?? \$bar ?? \$baz ?? \$qux// outputs 1

?>

### User Contributed Notes 44 notes

140
crazy888s at hotmail dot com
11 years ago
I couldn't find much info on stacking the new ternary operator, so I ran some tests:

<?php
echo 0 ?: 1 ?: 2 ?: 3; //1
echo 1 ?: 0 ?: 3 ?: 2; //1
echo 2 ?: 1 ?: 0 ?: 3; //2
echo 3 ?: 2 ?: 1 ?: 0; //3

echo 0 ?: 1 ?: 2 ?: 3; //1
echo 0 ?: 0 ?: 2 ?: 3; //2
echo 0 ?: 0 ?: 0 ?: 3; //3
?>

It works just as expected, returning the first non-false value within a group of expressions.
81
arnaud at arnapou dot net
10 years ago
[Editor's note: consider using ===]

I discover after 10 years of PHP development something awfull : even if you make a string comparison (both are strings), strings are tested like integers and leading "space" character (even \n, \r, \t) is ignored ....

I spent hours because of leading \n in a string ... it hurts my developper sensibility to see two strings beeing compared like integers and not like strings ... I use strcmp now for string comparison ... so stupid ...

Test code :
<?php

test
("1234", "1234");
test("1234", " 1234");
test("1234", "\n1234");
test("1234", "1234 ");
test("1234", "1234\n");

function
test(\$v1, \$v2) {
echo
"<h1>[".show_cr(\$v1)."] vs [".show_cr(\$v2)."]</h1>";
echo
my_var_dump(\$v1)."<br />";
echo
my_var_dump(\$v2)."<br />";
if(
\$v1 == \$v2) {
echo
"EQUAL !";
}
else {
echo
"DIFFERENT !";
}
}

function
show_cr(\$var) {
return
str_replace("\n", "\\n", \$var);
}

function
my_var_dump(\$var) {

ob_start();

var_dump(\$var);

\$dump = show_cr(trim(ob_get_contents()));

ob_end_clean();
return
\$dump;
}

?>

Displays this ->

[1234] vs [1234]
string(4) "1234"
string(4) "1234"
EQUAL !

[1234] vs [ 1234]
string(4) "1234"
string(5) " 1234"
EQUAL !

[1234] vs [\n1234]
string(4) "1234"
string(5) "\n1234"
EQUAL !

[1234] vs [1234 ]
string(4) "1234"
string(5) "1234 "
DIFFERENT !

[1234] vs [1234\n]
string(4) "1234"
string(5) "1234\n"
DIFFERENT !
46
Harry Willis
6 years ago
I was interested about the following two uses of the ternary operator (PHP >= 5.3) for using a "default" value if a variable is not set or evaluates to false:

<?php
(isset(\$some_variable) && \$some_variable) ? \$some_variable : 'default_value';

\$some_variable ?: 'default_value';
?>

The second is more readable, but will throw an ERR_NOTICE is \$some_variable is not set. Of course, this could be overcome by suppressing the notice using the @ operator.

Performance-wise, though, comparing 1 million iterations of the three statements

(isset(\$foo) && \$foo) ? \$foo : ''
(\$foo) ?: ''
(@\$foo) ?: ''

results in the following:

\$foo is NOT SET.
[isset] 0.18222403526306
[?:]    0.57496404647827
[@ ?:]  0.64780592918396
\$foo is NULL.
[isset] 0.17995285987854
[?:]    0.15304207801819
[@ ?:]  0.20394206047058
\$foo is FALSE.
[isset] 0.19388508796692
[?:]    0.15359902381897
[@ ?:]  0.20741701126099
\$foo is TRUE.
[isset] 0.17265486717224
[?:]    0.11773896217346
[@ ?:]  0.16193103790283

In other words, using the long-form ternary operator with isset(\$some_variable) is preferable overall if \$some_variable may not be set.

(error_reporting was set to zero for the benchmark, to avoid printing a million notices...)
37
jwhiting at hampshire dot edu
17 years ago
note: the behavior below is documented in the appendix K about type comparisons, but since it is somewhat buried i thought i should raise it here for people since it threw me for a loop until i figured it out completely.

just to clarify a tricky point about the == comparison operator when dealing with strings and numbers:

('some string' == 0) returns TRUE

however, ('123' == 0) returns FALSE

also note that ((int) 'some string') returns 0

and ((int) '123') returns 123

the behavior makes senes but you must be careful when comparing strings to numbers, e.g. when you're comparing a request variable which you expect to be numeric. its easy to fall into the trap of:

if (\$_GET['myvar']==0) dosomething();

as this will dosomething() even when \$_GET['myvar'] is 'some string' and clearly not the value 0

i was getting lazy with my types since php vars are so flexible, so be warned to pay attention to the details...
32
thomas dot oldbury at tgohome dot com
14 years ago
Be careful when using the ternary operator!

The following will not evaluate to the expected result:

<?php
echo "a string that has a " . (true) ? 'true' : 'false' . " condition in. ";
?>

Will print true.

<?php
echo "a string that has a " . ((true) ? 'true' : 'false') . " condition in. ";
?>

This will evaluate to the expected result: "a string that has a true condition in. "

I hope this helps.
33
mail at mkharitonov dot net
7 years ago
Be careful with the "==" operator when both operands are strings:
<?php
var_dump
('123' == '       123'); // true
var_dump('1e3' == '1000'); // true
var_dump('+74951112233' == '74951112233'); // true
var_dump('00000020' == '0000000000000000020'); // true
var_dump('0X1D' == '29E0'); // true
var_dump('0xafebac' == '11529132'); // true
var_dump('0xafebac' == '0XAFEBAC'); // true
var_dump('0xeb' == '+235e-0'); // true
var_dump('0.235' == '+.235'); // true
var_dump('0.2e-10' == '2.0E-11'); // true
var_dump('61529519452809720693702583126814' == '61529519452809720000000000000000'); // true in php < 5.4.4
19
jeronimo at DELETE_THIS dot transartmedia dot com
16 years ago
For converted Perl programmers: use strict comparison operators (===, !==) in place of string comparison operators (eq, ne). Don't use the simple equality operators (==, !=), because (\$a == \$b) will return TRUE in many situations where (\$a eq \$b) would return FALSE.

For instance...
"mary" == "fred" is FALSE, but
"+010" == "10.0" is TRUE (!)

In the following examples, none of the strings being compared are identical, but because PHP *can* evaluate them as numbers, it does so, and therefore finds them equal...

<?php

echo ("007" == "7" ? "EQUAL" : "not equal");
// Prints: EQUAL

// Surrounding the strings with single quotes (') instead of double
// quotes (") to ensure the contents aren't evaluated, and forcing
// string types has no effect.
echo ( (string)'0001' == (string)'+1.' ? "EQUAL" : "not equal");
// Prints: EQUAL

// Including non-digit characters (like leading spaces, "e", the plus
// or minus sign, period, ...) can still result in this behavior, if
// a string happens to be valid scientific notation.
echo ('  131e-2' == '001.3100' ? "EQUAL" : "not equal");
// Prints: EQUAL

?>

If you're comparing passwords (or anything else for which "near" precision isn't good enough) this confusion could be detrimental. Stick with strict comparisons...

<?php

// Same examples as above, using === instead of ==

echo ("007" === "7" ? "EQUAL" : "not equal");
// Prints: not equal

echo ( (string)'0001' === (string)'+1.' ? "EQUAL" : "not equal");
// Prints: not equal

echo ('  131e-2' === '001.3100' ? "EQUAL" : "not equal");
// Prints: not equal

?>
19
hiroh2k at yahoo dot com
16 years ago
if you want to use the ?: operator, you should be careful with the precedence.

Here's an example of the priority of operators:

<?php
echo 'Hello, ' . isset(\$i) ? 'my friend: ' . \$username . ', how are you doing?' : 'my guest, ' . \$guestusername . ', please register';
?>

This make "'Hello, ' . isset(\$i)" the sentence to evaluate. So, if you think to mix more sentences with the ?: operator, please use always parentheses to force the proper evaluation of the sentence.

<?php
echo 'Hello, ' . (isset(\$i) ? 'my friend: ' . \$username . ', how are you doing?' : 'my guest, ' . \$guestusername . ', please register');
?>

for general rule, if you mix ?: with other sentences, always close it with parentheses.
40
Anonymous
15 years ago
The following contrasts the trinary operator associativity in PHP and Java.  The first test would work as expected in Java (evaluates left-to-right, associates right-to-left, like if stmnt), the second in PHP (evaluates and associates left-to-right)

<?php

echo "\n\n######----------- trinary operator associativity\n\n";

function
trinaryTest(\$foo){

\$bar    = \$foo > 20

? "greater than 20"

: \$foo > 10

? "greater than 10"

: \$foo > 5

? "greater than 5"

: "not worthy of consideration";
echo
\$foo." =>  ".\$bar."\n";
}

echo
"----trinaryTest\n\n";
trinaryTest(21);
trinaryTest(11);
trinaryTest(6);
trinaryTest(4);

function
trinaryTestParens(\$foo){

\$bar    = \$foo > 20

? "greater than 20"

: (\$foo > 10

? "greater than 10"

: (\$foo > 5

? "greater than 5"

: "not worthy of consideration"));
echo
\$foo." =>  ".\$bar."\n";
}

echo
"----trinaryTestParens\n\n";
trinaryTestParens(21);
trinaryTestParens(11);
trinaryTest(6);
trinaryTestParens(4);

?>

Output:

######----------- trinary operator associativity

----trinaryTest

21 =>  greater than 5
11 =>  greater than 5
6 =>  greater than 5
4 =>  not worthy of consideration

----trinaryTestParens

21 =>  greater than 20
11 =>  greater than 10
6 =>  greater than 5
4 =>  not worthy of consideration
16
Jeremy Swinborne
9 years ago
Beware of the consequences of comparing strings to numbers.  You can disprove the laws of the universe.

echo ('X' == 0 && 'X' == true && 0 == false) ? 'true == false' : 'sanity prevails';

This will output 'true == false'.  This stems from the use of the UNIX function strtod() to convert strings to numbers before comparing.  Since 'X' or any other string without a number in it converts to 0 when compared to a number, 0 == 0 && 'X' == true && 0 == false
G
3 years ago
Do note, using the ternary operator shorthand (since 5.3), omitting the 2nd expression the first expression will only be called once.

Before 5.3 (or not using the shorthand)
<?php
\$val
= f('x') ? f('x') : false;
// f('x') will be run twice
?>

After 5.3
<?php
\$val
= f('x') ?: false;
// f('x') will be run once
?>
16
kapoor_rajiv at hotmail dot com
11 years ago
A quick way to do mysql bit comparison in php is to use the special character it stores . e.g
<?php

if (\$AvailableRequests['OngoingService'] == '')
echo
'<td>Yes</td>';
else
echo
'<td>No</td>';

?>
19
rshawiii at yahoo dot com
15 years ago
You can't just compare two arrays with the === operator
like you would think to find out if they are equal or not.  This is more complicated when you have multi-dimensional arrays.  Here is a recursive comparison function.

<?php
/**
* Compares two arrays to see if they contain the same values.  Returns TRUE or FALSE.
* usefull for determining if a record or block of data was modified (perhaps by user input)
* prior to setting a "date_last_updated" or skipping updating the db in the case of no change.
*
* @param array \$a1
* @param array \$a2
* @return boolean
*/
function array_compare_recursive(\$a1, \$a2)
{
if (!(
is_array(\$a1) and (is_array(\$a2)))) { return FALSE;}

if (!
count(\$a1) == count(\$a2))
{
return
FALSE; // arrays don't have same number of entries

}

foreach (
\$a1 as \$key => \$val)
{
if (!
array_key_exists(\$key, \$a2))
{return
FALSE; // uncomparable array keys don't match

}
elseif (
is_array(\$val) and is_array(\$a2[\$key]))  // if both entries are arrays then compare recursive

{if (!array_compare_recursive(\$val,\$a2[\$key])) return FALSE;
}
elseif (!(
\$val === \$a2[\$key])) // compare entries must be of same type.

{return FALSE;
}
}
return
TRUE; // \$a1 === \$a2
}
?>
18
gondo
6 years ago
beware of the fact, that there is no `<==` nor `>==` therefore `false <= 0` will be `true`. php v. 5.4.27
17
Alex
14 years ago
I think everybody should read carefully what "jeronimo at DELETE_THIS dot transartmedia dot com" wrote. It's a great pitfall even for seasoned programmers and should be looked upon with a great attention.
For example, comparing passwords with == may result in a very large security hole.

I would add some more to it:

The workaround is to use strcmp() or ===.

Note on ===:

While the php documentation says that, basically,
(\$a===\$b)  is the same as  (\$a==\$b && gettype(\$a) == gettype(\$b)),
this is not true.

The difference between == and === is that === never does any type conversion. So, while, according to documentation, ("+0.1" === ".1") should return true (because both are strings and == returns true), === actually returns false (which is good).
niall at maranelda dot org
3 years ago
Care must be taken when using the spaceship operator with arrays that do not have the same keys:

- Contrary to the notes above ("Example #2 Transcription of standard array comparison"), it does *not* return null if the left-hand array contains a key that the right-hand array does not.
- Because of this, the result depends on the order you do the comparison in.

For example:

<?php
\$a
= ['a' => 1, 'b' => 2, 'c' => 3, 'e' => 4];
\$b = ['a' => 1, 'b' => 2, 'd' => 3, 'e' => 4];

var_dump(\$a <=> \$b);        // int(1) : \$a > \$b because \$a has the 'c' key and \$b doesn't.

var_dump(\$b <=> \$a);        // int(1) : \$b > \$a because \$b has the 'd' key and \$a doesn't.
?>
14
Cuong Huy To
9 years ago
In the table "Comparison with Various Types", please move the last line about "Object" to be above the line about "Array", since Object is considered to be greater than Array (tested on 5.3.3)

(Please remove my "Anonymous" post of the same content before. You could check IP to see that I forgot to type my name)
18
14 years ago
Note: according to the spec, PHP's comparison operators are not transitive.  For example, the following are all true in PHP5:

"11" < "a" < 2 < "11"

As a result, the outcome of sorting an array depends on the order the elements appear in the pre-sort array.  The following code will dump out two arrays with *different* orderings:

<?php
\$a
= array(2,    "a""11", 2);
\$b = array(2,    "11", "a"2);
sort(\$a);
var_dump(\$a);
sort(\$b);
var_dump(\$b);
?>

This is not a bug report -- given the spec on this documentation page, what PHP does is "correct".  But that may not be what was intended...
13
bishop
14 years ago
When you want to know if two arrays contain the same values, regardless of the values' order, you cannot use "==" or "===".  In other words:

<?php
(array(1,2) == array(2,1)) === false;
?>

<?php
function array_equal(\$a, \$b) {
return (
is_array(\$a) && is_array(\$b) && array_diff(\$a, \$b) === array_diff(\$b, \$a));
}
?>

A related, but more strict problem, is if you need to ensure that two arrays contain the same key=>value pairs, regardless of the order of the pairs.  In that case, use:

<?php
function array_identical(\$a, \$b) {
return (
is_array(\$a) && is_array(\$b) && array_diff_assoc(\$a, \$b) === array_diff_assoc(\$b, \$a));
}
?>

Example:
<?php
\$a
= array (2, 1);
\$b = array (1, 2);
// true === array_equal(\$a, \$b);
// false === array_identical(\$a, \$b);

\$a = array ('a' => 2, 'b' => 1);
\$b = array ('b' => 1, 'a' => 2);
// true === array_identical(\$a, \$b)
// true === array_equal(\$a, \$b)
?>

17
stepheneliotdewey at gmail [period] com
14 years ago
Note that typecasting will NOT prevent the default behavior for converting two numeric strings to numbers when comparing them.

e.g.:

<?php
if ((string) '0123' == (string) '123')
print
'equals';
else
print
'doesn\'t equal';
?>

Still prints 'equals'

As far as I can tell the only way to avoid this is to use the identity comparison operators (=== and !==).
prezire at gmail dot com
5 years ago
Take note when grouping ternary operations that return either boolean or integer concatenated to a string:
<?php

echo 'hello ' . true ? 1 : 0, //Outputs 1

'hello ' . (true ? 1 : 0); //Outputs hello 1
?>
Sumon Mahmud
1 year ago
Extending from here: https://www.php.net/manual/en/language.operators.comparison.php#121907

\$a = ['a' => 1, 'b' => 2, 'c' => 3, 'e' => 4];
\$b = ['a' => 1, 'b' => 2, 'd' => 3, 'e' => 4];

echo \$a > \$b; // 0
echo \$b > \$a; // 0
echo \$a <\$b; // 0
echo \$b < \$a; // 0

If using spaceship operator then it is returning true like :

echo \$a <=> \$b; //1
echo \$b <=> \$a; //1
echo \$a <=> \$b; //1
echo \$b <=> \$a; //1
10
alan dot g at nospam dot net
10 years ago
a function to help settings default values, it returns its own first non-empty argument :

make your own eor combos !

<?php

/*
* Either Or
*
* usage:  \$foo = eor(test1(),test2(),"default");
* usage:  \$foo = eor(\$_GET['foo'], foogen(), \$foo, "bar");
*/

function eor() {

\$vars = func_get_args();
while (!empty(
\$vars) && empty(\$defval))

\$defval = array_shift(\$vars);
return
\$defval;
}

?>
13
Anonymous
11 years ago
Note: The ternary shortcut currently seems to be of no use in dealing with unexisting keys in an array, as PHP will throw an error. Take the following example.

<?php
\$_POST
['Unexisting'] = \$_POST['Unexisting'] ?: false;
?>

PHP will throw an error that the "Unexisting" key does not exist. The @ operator does not work here to suppress this error.
11
bimal at sanjaal dot com
8 years ago
I came across peculiar outputs while I was attempting to debug a script

<?php
# Setup platform (pre conditions somewhere in a loop)
\$index=1;
\$tally = array();

# May work with warnings that \$tally[\$index] is not initialized
# Notice: Undefined offset: 1 in D:\htdocs\colors\ColorCompare\i.php on line #__
# It is an old fashioned way.
# \$tally[\$index] = \$tally[\$index] + 1;

# Does not work: Loops to attempt to change \$index and values are aways unaffected
\$tally[\$index] = isset(\$tally[\$index])?\$tally[\$index]:0+1;
\$tally[\$index] = isset(\$tally[\$index])?\$tally[\$index]:0+1;
\$tally[\$index] = isset(\$tally[\$index])?\$tally[\$index]:0+1;
/*
# These three lines output:
Array
(
[1] => 1
)
*/

# Works: This is what I need/expect
# \$tally[\$index] = 1+(isset(\$tally[\$index])?\$tally[\$index]:0);

print_r(\$tally);
?>

The second block obviously does not work what one expects.
Third part is good.
13
fernandoleal at dragoncs dot com
14 years ago
If you need nested ifs on I var its important to group the if so it works.
Example:
<?php
//Dont Works
//Parse error: parse error, unexpected ':'
\$var='<option value="1" '.\$status == "1" ? 'selected="selected"' :''.'>Value 1</option>';
//Works:
\$var='<option value="1" '.(\$status == "1" ? 'selected="selected"' :'').'>Value 1</option>';

echo
\$var;
?>
10
Hayley Watson
14 years ago
Note that the "ternary operator" is better described as the "conditional operator". The former name merely notes that it has three arguments without saying anything about what it does. Needless to say, if PHP picked up any more ternary operators, this will be a problem.

"Conditional Operator" is actually descriptive of the semantics, and is the name historically given to it in, e.g., C.
Marcin Kuzawiski
5 years ago
A < B and still B < A...

\$A = [1 => 1, 2 => 0, 3 => 1];
\$B = [1 => 1, 3 => 0, 2 => 1];

var_dump(\$A < \$B);  // TRUE
var_dump(\$B < \$A);  // TRUE

var_dump(\$A > \$B);  // TRUE
var_dump(\$B > \$A);  // TRUE

Next - C and D are comparable, but neither C < D nor D < C (and still C != D)...

\$C = [1 => 1, 2 => 1, 3 => 0];
\$D = [1 => 1, 3 => 1, 2 => 0];

var_dump(\$C < \$D); // FALSE
var_dump(\$D < \$C); // FALSE

var_dump(\$C > \$D); // FALSE
var_dump(\$D > \$C); // FALSE

var_dump(\$D == \$C); // FALSE
Romain
2 years ago
?? vs isset() with __isset() and __get()

<?php

class A
{
public function
__get(\$id)
{
return
'a value';
}
}

class
B
{
public function
__isset(\$id)
{
return
false;
}

public function
__get(\$id)
{
return
'a value';
}
}

class
c
{
protected
\$test = "a value";

public function
__isset(\$id)
{
return
true;
}
}

\$a = new A();
\$b = new B();
\$c = new C();

echo isset(
\$a->test) ? \$a->test : 'nothing'; // "nothing"
echo \$a->test ?? 'nothing'; // "a value", isset() is not called!

echo isset(\$b->test) ? \$b->test : 'nothing'; // "nothing"
echo \$b->test ?? 'nothing'; // "nothing", __isset() is called

echo isset(\$c->test) ? \$c->test : 'nothing'; // throw an Exception
echo \$c->test ?? 'nothing'; // "nothing"

?>
Mark Simon
9 years ago
The use of 5.3’s shortened ternary operator allows PHP to coalesce a null or empty value to an alternative:

\$value = \$planA ?: \$planB;

My own server doesn’t yet run 5.3. A nice alternative is to use the “or” operator:

\$value = \$planA or \$value = planB;
user@example
17 years ago
With Nested ternary Operators you have to set the logical  parentheses to get the correct result.

<?php
\$test
=true;
\$test2=true;

(
\$test) ? "TEST1 true" :  (\$test2) ? "TEST2 true" : "false";
?>
This will output: TEST2 true;

correct:

<?php
\$test
=true;
\$test2=true;

(
\$test) ? "TEST1 true" : ((\$test2) ? "TEST2 true" : "false");
?>

Anyway don't nest them to much....!!
j-a-n at gmx dot de
9 years ago
Please be careful when comparing strings with floats, especally when you are using the , as decimal.

<?php
var_dump
(\$alt);
var_dump(\$neu);
var_dump(\$alt == \$neu);
?>

string(9) "590217,73"
float(590217,73)
bool(false)

not the float is cast to a string and then string-compared, but the string is cast to a float and then float-compared.

to compare as strings use strval!

<?php
var_dump
(strval(\$alt));
var_dump(strval(\$neu));
var_dump(strval(\$alt) == strval(\$neu));
?>

string(9) "590217,73"
string(9) "590217,73"
bool(true)
taras dot bogach at gmail dot com
11 years ago
Boolean switch usege

<?php
class User_Exception extends Exception{}
class
User{
public function
switch(
false){
case(
strlen(\$pass) >= 5):
throw new
User_Exception("Password must be at last 5 chars length");
case(
\$pass == \$passCheck):
throw new
case(
throw new
User_Exception("Login must be at last 5 chars length");

//Do other checks

default:

//Do registration

return true;
}
}

//...
}
?>
zak at minion dot net
9 years ago
be careful when trying to concatenate the result of a ternary operator to a string

<?php
print
'<br><br>';
print
'<div>'.((FALSE) ? 'TRUE [good ternary]' : 'FALSE [good ternary]');
?>

yields:

FALSE [good ternary]

this is because the ternary evaluates '<div>'.(FALSE) not (FALSE) - so the end result is TRUE
damien dot launay dot mail at gmail dot com
7 years ago
I found a nice way to use of new "?:" operator:

\$a = array();
\$a['foo'] = 'oof';

\$b = @ (\$a['foo'] ?: 'No foo');
\$c = @ (\$a['bar'] ?: 'No bar');

var_dump(\$b, \$c);

Output:

string(3) "oof"
string(6) "No bar"

No error is thrown and \$c is set with correct value.

Benefit: no need to use isset.
Ryan Mott
1 year ago
Searching for "double question mark" operator should find this page (and hopefully after this comment the crawlers will agree)
sgurukrupa at gmail dot com
6 years ago
With respect to using the ternary operator as a 'null-coalescing' operator: expr1 ?: expr2, note that expr1 is evaluated only once.
mail at markuszeller dot com
10 years ago
I prefer writing (!\$a == 'hello') much more than (\$a != 'hello'), but I wondered about the performance.

So I did a benchmark:
<?php
for(\$bench = 0; \$bench < 3; \$bench++)
{

\$start = microtime(true);

\$a = 1;
for(
\$i = 0; \$i < 100000000; \$i++)
{
if(!
\$a == 'hello') \$b++;
}

\$end = microtime(true);
echo
"Used time: " . (\$end-\$start) . "\n";
}
?>
and it results with

# if(\$a != 'hello')
Used time: 12.552895069122
Used time: 12.548940896988
Used time: 12.470285177231

# if(!\$a == 'hello')
Used time: 7.6532161235809
Used time: 7.6426539421082
Used time: 7.6452689170837
halfhearted13 at gmail dot com
7 months ago
Both Null Coalescing ( ?? ) and Ternary ( ? : ) can work at a time.

<?php

\$a
= "user name";
echo
\$a = null ?? \$a ? "sb" : "not found"; // it prints : sb
//as null coalescing has null on left it goes to 2nd expr \$a. \$a is defined so //output will be the 1st expr of Ternay operator.
?>

<?php

// null coalescing has empty value of its left. so it prints right expr which is //also empty. so the output will be the 2nd expr of ternary(written in short)

?>

<?php
echo \$x = "" ?? "" ?? "" ? : false// prints nothing.
// if you add var_dump() you see bool(false)
?>
instatiendaweb at gmail dot com
1 month ago
switch ("a") {
case 0:
echo "0";
break;
case "a": // nunca alcanzado debido a que "a" ya ha coincidido con 0
echo "a";
break;
}
In php 8.0 is echo "a";
yiminrong at yahoo dot ca
2 months ago
The string equality operator has a big gotcha in that if both operators match the format /^0+[Ee][0-9]+\$/, then the values will be considered equal. All these, which represent common use cases, will output true:

echo '0e56' == '0E31'; // comparing short hex strings
echo md5('240610708') == md5('QNKCDZO'); // comparing hashes - see comment by Ray Paseur in md5 function
echo '000e123' == '00e0123'; // permutation of a string

The reason is that strings in the format /^0+[Ee][0-9]+\$/ are interpreted as a number in scientific notation and zero raised to any power is zero.

Unless it is certain that the string will not match the specific format, then === should be used instead of == for strings.
itsacon at itsacon dot net
4 months ago
Be aware that the null coalesce operator (??) has a lower priority than most other operators, so parentheses are usually a good idea if the output is used in anything other than an assignment.

<?php
\$var
= 1;
if (
\$var ?? 0 == 2) {}  // will evaluate to true

if (2 == \$undefinedVar ?? 0) {}  // will throw an error

if ((\$var ?? 0) == 2) {}  // will evaluate to false
?>

https://www.php.net/manual/en/language.operators.precedence.php
Ireneusz Pachulski
4 months ago
Note that spaceship operator (<=>) is binary safe.

<?php
\$a
= "Hello";
\$b = "Hello\x00World";

echo (
\$a <=> \$b) . "<br>"; // -1
echo strcmp(\$a, \$b) . "<br>"; // -6
echo strcoll(\$a, \$b) . "<br>"; // 0 => not binary safe
?>
azz
1 year ago
Keep in mind that ?: operator is NOT fully equal to empty()

?: can't check non-existent array index (as describe here https://www.php.net/manual/ru/language.operators.comparison.php#92685) and vars

Check this:

<?php
ini_set
('error_reporting', E_ALL);

\$t = [];

var_dump(!isset(\$t['z']) || \$t['z'] == FALSE); // true, this that empty() do
var_dump(empty(\$t['z'])); // true
var_dump(isset(\$t['z'])); // false

\$v1 = \$t['z'] ?: false; // Notice:  Undefined index: z
\$v2 = \$t['z'] ?? false; // silent!

var_dump(\$v1); // false
var_dump(\$v2); // false

var_dump(!isset(\$non_existent_var) || \$non_existent_var == FALSE); // true, this that empty() do
var_dump(empty(\$non_existent_var)); // true
var_dump(isset(\$non_existent_var)); // false

\$v1 = \$non_existent_var ?: false; // Notice:  Undefined variable: non_existent_var
\$v2 = \$non_existent_var ?? false; // silent!

var_dump(\$v1); // false
var_dump(\$v2); // false