src/Language/Lexer.php
protected function char2hex($a)
    {
        return
            $a >= 48 && $a <= 57 ? $a - 48 : // 0-9
                ($a >= 65 && $a <= 70 ? $a - 55 : // A-F
                    ($a >= 97 && $a <= 102 ? $a - 87 : -1)); // a-f
    }
protected function char2hex($a)
    {
        return
            $a >= 48 && $a <= 57 ? $a - 48 : // 0-9
                ($a >= 65 && $a <= 70 ? $a - 55 : // A-F
                    ($a >= 97 && $a <= 102 ? $a - 87 : -1)); // a-f
    }
protected function char2hex ( $ a ) { return $ a >= 48 && $ a <= 57 ? $ a - 48 : // 0-9 ( $ a >= 65 && $ a <= 70 ? $ a - 55 : // A-F ( $ a >= 97 && $ a <= 102 ? $ a - 87 : - 1 ) ) ; // a-f }
Converts a hex character to its integer value.
'0' becomes 0, '9' becomes 9
'A' becomes 10, 'F' becomes 15
'a' becomes 10, 'f' becomes 15

Returns -1 on error.

@param $a

@return int
Converts a hex character to its integer value . 0 becomes 0 9 becomes 9 A becomes 10 F becomes 15 a becomes 10 f becomes 15