using |= in php

Question

I was reading some php code source and found the following:

$failed |= is_numeric( $key );

Other than if $key is numeric , what does |= mean?

Answer 1

$x |= $y; is the same as $x = $x | $y;

$x | $y is a bitwise operator which means it returns the result of a logical 'or' between the two variables.

In the context of the question, it allows $failed to store failure statuses for several actions in a single variable (each bit position representing an individual action).

If you need to know more about what this does, I suggest reading the PHP manual page for bitwise operators: http://www.php.net/manual/en/language.operators.bitwise.php