Example of php implementing the sunday algorithm of string matching algorithm

<?php

/*

 *@param $pattern 模式串

 *@param $text 待匹配串

 */

function mySunday($pattern = '',$text = ''){

    if(!$pattern || !$text) return false;

    $pattern_len = mb_strlen($pattern);

    $text_len = mb_strlen($text);

    if($pattern_len >= $text_len) return false;

    $i = 0;

    for($i = 0; $i < $pattern_len; $i++){ //组装以pattern中的字符为下标的数组

        $shift[$pattern[$i]] = $pattern_len - $i;

    }

    while($i <= $text_len - $pattern_len){

        $nums = 0;     //匹配上的字符个数

        while($pattern[$nums] == $text[$i + $nums]){

            $nums++;

            if($nums == $pattern_len){

                return "The first match index is $i\n";

            }

        }

        if($i + $pattern_len < $text_len && isset($shift[$text[$i + $pattern_len]])){ //判断模式串后一位字符是否在模式串中

            $i += $shift[$text[$i + $pattern_len]];      //对齐该字符

        }else{

            $i += $pattern_len;      //直接滑动pattern_len位

        }

    }

}

$text = "I am testing mySunday on sunday!";

$pattern = "sunday";

echo mySunday($pattern,$text);