Bit-shift PHP strings.

gistfile1.php

<?php

    function str_left_shift($str, $count) {
        $bytes = floor($count / 8);

        if ($bytes) {
            $str = substr($str, $bytes)
                 . str_repeat("\x00", $bytes);

            $count = $count % 8;
        }

        $flip = 8 - $count;
        $base = 0xff << $flip;
        $carryLeft = $carryRight = 0;
        
        for ($i = strlen($str) - ++$bytes; $i >= 0; $i--) {
            $char = ord($str[$i]);
            $carryLeft = ($char & $base) >> $flip;
            $str[$i] = chr(($char << $count) | $carryRight);
            $carryRight = $carryLeft;
        }

        return $str;
    }

    function str_right_shift($str, $count) {
        $bytes = floor($count / 8);

        if ($bytes) {
            $str = str_repeat("\x00", $bytes)
                 . substr($str, 0, $bytes * -1);

            $count = $count % 8;
        }

        $flip = 8 - $count;
        $base = 0xff >> $flip;
        $carryLeft = $carryRight = 0;
        
        for ($i = $bytes, $l = strlen($str); $i < $l; $i++) {
            $char = ord($str[$i]);
            $carryLeft = ($char & $base) << $flip;
            $str[$i] = chr(($char >> $count) | $carryRight);
            $carryRight = $carryLeft;
        }

        return $str;
    }