What does ^ mean in PHP?

I came across this line of code in an application I am revising:

substr($sometext1 ^ $sometext2, 0, 512);

What does the ^ mean?

Answer

It's a bitwise operator.

Example:

"hallo" ^ "hello"

It outputs the ASCII values #0 #4 #0 #0 #0 ('a' ^ 'e' = #4).