Operator '?'

[borris83]

Is there any operator that has '?' sign in php? If yes, then what is that for?

I am trying to understand some source code, and the statement is:


$app_root_path = (defined('APP_ROOT_PATH')) ? APP_ROOT_PATH : './';

Can you also explain the statement completely and what it does

[JasonDFR]

It is called the ternary operator.


// something to evaluate ? 'value if true' : 'value if false';

$t = 'A';
//$t = 'B';
echo preg_match('/A/', $t) ? 'match' : 'no match';



Used inside the echo statement above, it says: Depending on whether or not preg_match() is true or false (1 or 0), echo match or no match. If preg_match() returns 1, the word 'match' is echoed. If preg_match() returns 0, the words 'no match' will be echoed.

Used inside your example, it says, if the constant APP_ROOT_PATH has been defined, set the $app_root_path variable equal to the value of the APP_ROOT_PATH constant. If APP_ROOT_PATH has not been defined, set the variable to './' Since the function defined() returns true or false, the ternary operator (?) can either use the first value after it if true, or the second, if false.

[codeexploiter]

Terenary operator can be thought of as a simple if else construct:

The syntax:

[your_variable = ] expression ? true part : false part;

If your expression is evaluated to true then it will execute the true part or the false part.

[Twey]

More importantly, it returns the true or false part. Unlike the if statement, the ternary conditional operator forms an expression.

[borris83]

Thank you all, Very informative... I searched for it in php.net... I don't know what keyword to use, and hence I searched for 'operators', but it wasn't listed there...

Cool! I never thought that I could write an 'IF ELSE' statement this way

[Twey]

It's on the comparison operators (http://www.php.net/operators.comparison) page, at the bottom of the article.