Question

In PHP, if there is a conditional like this:

if ( is_numeric($my_var) && $my_var == 1 ) {

}

If the first part of the if is false, does the second part ($my_var == 1) get ever executed?

Thanks!

Answer 1

In your example the $my_var == 1 will not be executed (if it’s not numeric). PHP will determinate that the first part evaluated to false and so there is no benefit in executing the second part because you are using the && AND operator.

An example:

if(isset($_GET['something']) && $_GET['something'] == '1')
{

}

If the querystring variable something is missing then it doesn’t check if it equals 1. If it did then it could produce an Undefined index notice.

You can also verify this behavior with something like:

$test = '2';
if($test == '1' && die('dead'))
{

}

echo 'execution continues....';

Set $test = '2' and the die() will not stop execution. Set it to 1 and the die will execute and stop, thus you won’t see Execution continues...

Edit: there is some general information here (not PHP specific).