In PHP what does |= mean, That is pipe equals (not exclamation)

Question

I just found this in some code and I can\'t find anything on the web or php manual. Most likely since its an irregular character.

Here is one of the lines that uses

Answer 1

|= is to | as += is to +; that is, $a |= $b; is the same as $a = $a | $b;. The | operator is the bitwise OR operator.