To prevent an accidental assignment when comparing two variables, wrap the first one within parentheses.

tips1.php

<?php

$foo = 10; $bar = 9;

var_dump($foo = $bar); // whoops, accidental assignment! but no message will be displayed

var_dump(($foo) = $bar); // again, but this is a syntax error b/c an expression can't have a value assigned to it!