PHP实例：PHP改进计算字符串相似度的函数similar_text()、levenshtein()

     <?php 
     //拆分字符串 
     function split_str($str) { 
       preg_match_all("/./u", $str, $arr); 
       return $arr[0]; 
     } 
      
     //相似度检测 
     function similar_text_cn($str1, $str2) { 
       $arr_1 = array_unique(split_str($str1)); 
       $arr_2 = array_unique(split_str($str2)); 
       $similarity = count($arr_2) - count(array_diff($arr_2, $arr_1)); 
        
       return $similarity; 
     }  

     <?php 
     //拆分字符串 
     function mbStringToArray($string, $encoding = 'UTF-8') { 
         $arrayResult = array(); 
         while ($iLen = mb_strlen($string, $encoding)) { 
             array_push($arrayResult, mb_substr($string, 0, 1, $encoding)); 
             $string = mb_substr($string, 1, $iLen, $encoding); 
         } 
         return $arrayResult; 
     } 
     //编纂距离 
     function levenshtein_cn($str1, $str2, $costReplace = 1, $encoding = 'UTF-8') { 
         $count_same_letter = 0; 
         $d = array(); 
         $mb_len1 = mb_strlen($str1, $encoding); 
         $mb_len2 = mb_strlen($str2, $encoding); 
         $mb_str1 = mbStringToArray($str1, $encoding); 
         $mb_str2 = mbStringToArray($str2, $encoding); 
         for ($i1 = 0; $i1 <= $mb_len1; $i1++) { 
             $d[$i1] = array(); 
             $d[$i1][0] = $i1; 
         } 
         for ($i2 = 0; $i2 <= $mb_len2; $i2++) { 
             $d[0][$i2] = $i2; 
         } 
         for ($i1 = 1; $i1 <= $mb_len1; $i1++) { 
             for ($i2 = 1; $i2 <= $mb_len2; $i2++) { 
                 // $cost = ($str1[$i1 - 1] == $str2[$i2 - 1]) ? 0 : 1; 
                 if ($mb_str1[$i1 - 1] === $mb_str2[$i2 - 1]) { 
                     $cost = 0; 
                     $count_same_letter++; 
                 } else { 
                     $cost = $costReplace; //替换 
                 } 
                 $d[$i1][$i2] = min($d[$i1 - 1][$i2] + 1, //插入 
                 $d[$i1][$i2 - 1] + 1, //删除 
                 $d[$i1 - 1][$i2 - 1] + $cost); 
             } 
         } 
         return $d[$mb_len1][$mb_len2]; 
         //return array('distance' => $d[$mb_len1][$mb_len2], 'count_same_letter' => $count_same_letter); 
     }  

         <?php 
         //最长公共子序列英文版 
         function LCS_en($str_1, $str_2) { 
           $len_1 = strlen($str_1); 
           $len_2 = strlen($str_2); 
           $len = $len_1 > $len_2 ? $len_1 : $len_2; 
           $dp = array(); 
           for ($i = 0; $i <= $len; $i++) { 
             $dp[$i] = array(); 
             $dp[$i][0] = 0; 
             $dp[0][$i] = 0; 
           } 
           for ($i = 1; $i <= $len_1; $i++) { 
             for ($j = 1; $j <= $len_2; $j++) { 
               if ($str_1[$i - 1] == $str_2[$j - 1]) { 
                 $dp[$i][$j] = $dp[$i - 1][$j - 1] + 1; 
               } else { 
                 $dp[$i][$j] = $dp[$i - 1][$j] > $dp[$i][$j - 1] ? $dp[$i - 1][$j] : $dp[$i][$j - 1]; 
               } 
             } 
           } 
           return $dp[$len_1][$len_2]; 
         } 
         //拆分字符串 
         function mbStringToArray($string, $encoding = 'UTF-8') { 
           $arrayResult = array(); 
           while ($iLen = mb_strlen($string, $encoding)) { 
             array_push($arrayResult, mb_substr($string, 0, 1, $encoding)); 
             $string = mb_substr($string, 1, $iLen, $encoding); 
           } 
           return $arrayResult; 
         } 
         //最长公共子序列中文版 
         function LCS_cn($str1, $str2, $encoding = 'UTF-8') { 
           $mb_len1 = mb_strlen($str1, $encoding); 
           $mb_len2 = mb_strlen($str2, $encoding); 
           $mb_str1 = mbStringToArray($str1, $encoding); 
           $mb_str2 = mbStringToArray($str2, $encoding); 
           $len = $mb_len1 > $mb_len2 ? $mb_len1 : $mb_len2; 
           $dp = array(); 
           for ($i = 0; $i <= $len; $i++) { 
             $dp[$i] = array(); 
             $dp[$i][0] = 0; 
             $dp[0][$i] = 0; 
           } 
           for ($i = 1; $i <= $mb_len1; $i++) { 
             for ($j = 1; $j <= $mb_len2; $j++) { 
               if ($mb_str1[$i - 1] == $mb_str2[$j - 1]) { 
                 $dp[$i][$j] = $dp[$i - 1][$j - 1] + 1; 
               } else { 
                 $dp[$i][$j] = $dp[$i - 1][$j] > $dp[$i][$j - 1] ? $dp[$i - 1][$j] : $dp[$i][$j - 1]; 
               } 
             } 
           } 
           return $dp[$mb_len1][$mb_len2]; 
         }