PHP tokenizer resolves bitwise xor operator as power operator

[smatyas]

The exponentiation arithmetic operator in PHP is **, and only exists since PHP 5.6
The ^ operator is only the bitwise XOR operator.

See:
http://php.net/manual/en/language.operators.arithmetic.php
http://php.net/manual/en/language.operators.bitwise.php

The wrong code is here: https://github.com/squizlabs/PHP_CodeSniffer/blob/master/CodeSniffer/Tokenizers/PHP.php#L1307

        case '^':
            $newToken['type'] = 'T_POWER';
            break;

I'm not familiar enough with PHP_CodeSniffer's code yet, so I cannot make a PR now, but I'm sure that this is a tokenizer bug.

[gsherwood]

I'm pretty sure that's always been like that, and I have no idea why. Thanks for picking it up.

[smatyas]

Thanks for the fix, great work! :)