php代码把全角数字转为半角数字

//把全角数字转为半角数字
function GetAlabNum（$fnum）{
    $nums = array（"０","１","２","３","４","５","６","７","８","９","．","－","＋","："）;
    $fnums = array（"0","1",  "2","3",  "4","5",  "6", "7","8",  "9",".",  "-", "+",":"）;
    $fnlen = count（$fnums）;
    for（$i=0;$i<$fnlen;$i++） $fnum = str_replace（$nums[$i],$fnums[$i],$fnum）;
    $slen = strlen（$fnum）;
    $oknum = "";
    for（$i=0;$i<$slen;$i++）{
        if（ord（$fnum[$i]） > 0x80） $i++;
        else $oknum .= $fnum[$i];
    }
    if（$oknum==""） $oknum=0;
    return $oknum;
}