PHP implementation KMP algorithm

function Cal_next ($str) {    $next [0] = -1;//next[0] is initialized to-1    $i =0;    $j =-1;    $len =strlen ($STR);    while ($i < $len) {            if ($j ===-1 | | $str [$i]=== $str [$j]) {            $i + +;            $j + +;            $next [$i]= $j;        } else{            $j = $next [$j];        }    }    return $next;} $str = ' abcdabd '; $next =cal_next ($STR); Var_dump ($next); function search ($STR, $search) {    $next =cal_next ($search) ;    $i =0;    $j =0;    $lenStr =strlen ($STR);    $lenSearch =strlen ($search);    while ($i < $lenStr && $j < $lenSearch) {            if ($j ===-1 | | $str [$i]=== $search [$j]) {            //$i The main string does not retreat, Move the pattern string. Why there is no $j===0, because if there is $j++ for 1, the next step is to judge $str[$i]=== $search [1], skipped $search[0]            $i + +;            $j + +;        } else{            $j = $next [$j];        }    }    if ($j = = = $lenSearch) {        return $i-$j;    }    return-1;} Var_dump (Search ($str, ' ABD '));

Reference

[KMP Algorithm (1): How to understand KMP] (https://segmentfault.com/a/1190000008575379) [KMP algorithm for string matching] (http://www.ruanyifeng.com/blog/2013/05/Knuth%E2%80%93Morris%E2%80%93Pratt_algorithm.html) [KMP algorithm is the most superficial understanding] (https://blog.csdn.net/starstar1992/article/details/54913261)

function Cal_next ($str) {    $next [0] = -1;//next[0] is initialized to-1    $i =0;    $j =-1;    $len =strlen ($STR);    while ($i < $len) {        if ($j ===-1 | | $str [$i]=== $str [$j]) {            $i + +;            $j + +;            $next [$i]= $j;        } else{            $j = $next [$j];        }    }    return $next;} $str = ' abcdabd '; $next =cal_next ($STR); Var_dump ($next); function search ($STR, $search) {    $next =cal_next ($search) ;    $i =0;    $j =0;    $lenStr =strlen ($STR);    $lenSearch =strlen ($search);    while ($i < $lenStr && $j < $lenSearch) {        if ($j ===-1 | | $str [$i]=== $search [$j]) {//$i the main string does not rewind, move the mode string. Why there is no $j===0, because if there is $j++ for 1, the next step is to judge $str[$i]=== $search [1], skipped $search[0]            $i + +;            $j + +;        } else{            $j = $next [$j];        }    }    if ($j = = = $lenSearch) {        return $i-$j;    }    return-1;} Var_dump (Search ($str, ' ABD '));

Reference

[KMP Algorithm (1): How to understand KMP] (https://segmentfault.com/a/1190000008575379) [ KMP algorithm for string matching] (http://www.ruanyifeng.com/blog/2013/05/Knuth%E2%80%93Morris%E2%80%93Pratt_algorithm.html) [ KMP algorithm is the most superficial understanding] (https://blog.csdn.net/starstar1992/article/details/54913261)