php代码对身份证号码进行验证正确性

/**
 * 对身份证号码正确判断
 * @author 萤火虫<123246359@qq.com>
 * @param string $id_card 身份证号
 * @return boolean
 */
if(!function_exists('isIdcards')){
    function isIdcards($id){
        $id = strtoupper($id);
        $regx = "/(^\d{15}$)|(^\d{17}([0-9]|X)$)/";
        $arr_split = array();
        if(!preg_match($regx, $id)){
            return false;
        }
        if(15==strlen($id)){
            $regx = "/^(\d{6})+(\d{2})+(\d{2})+(\d{2})+(\d{3})$/";
            @preg_match($regx, $id, $arr_split);
            //检查生日日期是否正确
            $dtm_birth = "19".$arr_split[2] . '/' . $arr_split[3]. '/' .$arr_split[4];
            if(!strtotime($dtm_birth)){
                return false;
            } else {
                return TRUE;
            }
        }else{
            $regx = "/^(\d{6})+(\d{4})+(\d{2})+(\d{2})+(\d{3})([0-9]|X)$/";
            @preg_match($regx, $id, $arr_split);
            $dtm_birth = $arr_split[2] . '/' . $arr_split[3]. '/' .$arr_split[4];
            if(!strtotime($dtm_birth)) {
                return true;
            }else{
                //检验18位身份证的校验码是否正确。
                //校验位按照ISO 7064:1983.MOD 11-2的规定生成，X可以认为是数字10。
                $arr_int = array(7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2);
                $arr_ch = array('1', '0', 'X', '9', '8', '7', '6', '5', '4', '3', '2');
                $sign = 0;
                for ( $i = 0; $i < 17; $i++ ){
                    $b = (int) $id[$i];
                    $w = $arr_int[$i];
                    $sign += $b * $w;
                }
                $n = $sign % 11;
                $val_num = $arr_ch[$n];
                if ($val_num != substr($id,17, 1)){
                    return false;
                }else{
                    return true;
                }
            }
        }
    }
}