PHP syntax question: What does the question mark and colon mean?

Question

return $add_review ? FALSE : $arg;

What do question mark and colon mean?

Not to nitpick but isn't it the colon you want to know about and not the semicolon? Talking of colons, is this comment a tad anal? :-) — Jamie Dixon, Aug 14 '09 at 10:35
This question has a better title than the one it is marked as a duplicate of... — squarecandy, Sep 01 '13 at 19:42
Speaking from the future, 6 years later, this is the question I landed at. Thanks @PaulDixon for thinking of the people searching in the future. — MattWithoos, Nov 23 '15 at 02:48
@GregHewgill The accepted answer is better, even if the question is the same. — cartbeforehorse, Oct 22 '17 at 17:13

score 174 · Accepted Answer · edited Jan 15 '22 at 16:20

174

This is the PHP ternary operator (also known as a conditional operator) - if first operand evaluates true, evaluate as second operand, else evaluate as third operand.

Think of it as an "if" statement you can use in expressions. Can be very useful in making concise assignments that depend on some condition, e.g.

$param = isset($_GET['param']) ? $_GET['param'] : 'default';

There's also a shorthand version of this (in PHP 5.3 onwards). You can leave out the middle operand. The operator will evaluate as the first operand if it true, and the third operand otherwise. For example:

$result = $x ?: 'default';

It is worth mentioning that the above code when using i.e. $_GET or $_POST variable will throw undefined index notice and to prevent that we need to use a longer version, with isset or a null coalescing operator which is introduced in PHP7:

$param = $_GET['param'] ?? 'default';

edited Jan 15 '22 at 16:20

Undesirable

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answered Aug 14 '09 at 09:27

Paul Dixon

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Since PHP 5.3, it is also possible to leave out the middle part of the ternary operator. Expression `expr1 ?: expr3` returns `expr1` if `expr1` evaluates to TRUE, and `expr3` otherwise. – Chandrew Dec 17 '14 at 19:15
1

is there a situation in php7+ where you would want to use `?:` instead of `??`? – user Feb 17 '22 at 22:27
@user When `expr1` is not `NULL` but falsy instead (`FALSE`, `0`, etc). – Digitalam Aug 08 '22 at 09:43

score 22 · Answer 2 · answered Aug 14 '09 at 09:34

22

It's the ternary form of the if-else operator. The above statement basically reads like this:

if ($add_review) then {
    return FALSE; //$add_review evaluated as True
} else {
    return $arg //$add_review evaluated as False
}

See here for more details on ternary op in PHP: http://www.addedbytes.com/php/ternary-conditionals/

answered Aug 14 '09 at 09:34

Cristian Ivascu

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Sorry trying to understand this @cristianivascu how would this read - – Getsomepeaches Jul 13 '16 at 13:07
1

If the value in $active_page equals the string 'home' it would print out 'active', otherwise it would print an empty string. – Cristian Ivascu Jul 19 '16 at 23:45

PHP syntax question: What does the question mark and colon mean?

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