用PHP解码PDU编码的SMS

<?php
/**
 * Decode 7-bit packed PDU messages
 */
if ( !function_exists( 'hex2bin' ) ) {
    // pre 5.4 fallback
    function hex2bin( $str ) {
        $sbin = "";
        $len = strlen( $str );
        for ( $i = 0; $i < $len; $i += 2 ) {
            $sbin .= pack( "H*", substr( $str, $i, 2 ) );
        }

        return $sbin;
    }
}

function pdu2str($pdu) {
    // chop and store bytes
    $number = 0;
    $bitcount = 0;
    $output = '';
    while (strlen($pdu)>1) {
        $byte = ord(hex2bin(substr($pdu,0,2)));
        $pdu=substr($pdu, 2);
        $number += ($byte << $bitcount);
        $bitcount++ ;
        $output .= chr($number & 0x7F);
        $number >>= 7;
        if (7 == $bitcount) {
            // save extra char
            $output .= chr($number);
            $bitcount = $number = 0;
        }
    }
    return $output;
}

?>

function DecodePDU($sString = '')
{
    $sString = pack("H*",$sString);
    $sString = mb_convert_encoding($sString,'UTF-8','UCS-2');

    return $sString;
}