Shorthand conditional to define a variable based on the existence of another variable in PHP

php variables conditional shorthand
Ben Saufley picture Ben Saufley · Sep 17, 2010 · Viewed 20.8k times · Source

Essentially, I'd love to be able to define a variable as one thing unless that thing doesn't exist. I swear that somewhere I saw a shorthand conditional that looked something like this:

$var=$_GET["var"] || "default";

But I can't find any documentation to do this right, and honestly it might have been JS or ASP or something where I saw it.

I understand that all that should be happening in the above code is just to check if either statement returns true. But I thought I saw someone do something that essentially defined a default if the first failed. Is this something anyone knows about and can help me? Am I crazy? It just seems redundant to say:

$var=($_GET["var"]) ? $_GET["var"] : "default";

or especially redundant to say:

if ($_GET["var"]) { $var=$_GET["var"]; } else { $var="default"; }

Thoughts?

Answer

Matthew picture Matthew · Sep 17, 2010

Matthew has already mentioned the only way to do it in PHP 5.3. Note that you can also chain them:

$a = false ?: false ?: 'A'; // 'A'

This is not the same as:

$a = false || false || 'A'; // true

The reason why is that PHP is like most traditional languages in this aspect. The logical OR always returns true or false. However, in JavaScript, the final expression is used. (In a series of ORs, it will be the first non-false one.)

var a = false || 'A' || false; // 'A' 
var b = true && 'A' && 'B';    // 'B';

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