<?php
function hex2bin($hexdata) {
    $bindata = '';
    for($i=0; $i < strlen($hexdata); $i += 2) {
        $bindata .= chr(hexdec(substr($hexdata, $i, 2)));
    }
    return $bindata;
}
print hex2bin('ced2cac7d6d0b9fac8cb');
print "\n---------------------\n";
print bin2hex('我是中国人');
print "\n---------------------\n";