我刚刚找到了same_text函数，并且一直在使用它，但是输出百分比总是令我惊讶。请参阅下面的示例。

我试图找到有关在php：similar_text()
Docs 上使用的算法的信息：

<?php
$p = 0;
similar_text('aaaaaaaaaa', 'aaaaa', $p);
echo $p . "<hr>";
//66.666666666667
//Since 5 out of 10 chars match, I would expect a 50% match

similar_text('aaaaaaaaaaaaaaaaaaaa', 'aaaaa', $p);
echo $p . "<hr>";
//40
//5 out of 20 > not 25% ?

similar_text('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa', 'aaaaa', $p);
echo $p . "<hr>"; 
//9.5238095238095 
//5 out of 100 > not 5% ?


//Example from PHP.net
//Why is turning the strings around changing the result?

similar_text('PHP IS GREAT', 'WITH MYSQL', $p);
echo $p . "<hr>"; //27.272727272727

similar_text('WITH MYSQL', 'PHP IS GREAT', $p);
echo $p . "<hr>"; //18.181818181818

?>

谁能解释这是如何工作的？

更新：

多亏了这些评论，我发现该百分比实际上是使用相似字符的数量* 200 /长度1 +长度2计算得出的

Z_DVAL_PP(percent) = sim * 200.0 / (t1_len + t2_len);

因此，这解释了为什么敏锐度高于预期的原因。对于95中有5个的字符串，结果为10，所以我可以使用。

similar_text('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa', 'aaaaa', $p);
echo $p . "<hr>"; 
//10
//5 out of 95 = 5 * 200 / (5 + 95) = 10

但是我仍然不知道为什么PHP在翻转字符串时会返回不同的结果。dfsq提供的JS代码不会执行此操作。查看PHP中的源代码，我只能在以下几行中找到不同之处，但我不是交流程序员。一些区别的见解，将不胜感激。

在JS中：

for (l = 0;(p + l < firstLength) && (q + l < secondLength) && (first.charAt(p + l) === second.charAt(q + l)); l++);

在PHP中：（php_similar_str函数）

for (l = 0; (p + l < end1) && (q + l < end2) && (p[l] == q[l]); l++);

资源：

/* {{{ proto int similar_text(string str1, string str2 [, float percent])
   Calculates the similarity between two strings */
PHP_FUNCTION(similar_text)
{
  char *t1, *t2;
  zval **percent = NULL;
  int ac = ZEND_NUM_ARGS();
  int sim;
  int t1_len, t2_len;

  if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "ss|Z", &t1, &t1_len, &t2, &t2_len, &percent) == FAILURE) {
    return;
  }

  if (ac > 2) {
    convert_to_double_ex(percent);
  }

  if (t1_len + t2_len == 0) {
    if (ac > 2) {
      Z_DVAL_PP(percent) = 0;
    }

    RETURN_LONG(0);
  }

  sim = php_similar_char(t1, t1_len, t2, t2_len);

  if (ac > 2) {
    Z_DVAL_PP(percent) = sim * 200.0 / (t1_len + t2_len);
  }

  RETURN_LONG(sim);
}
/* }}} */


/* {{{ php_similar_str
 */
static void php_similar_str(const char *txt1, int len1, const char *txt2, int len2, int *pos1, int *pos2, int *max)
{
  char *p, *q;
  char *end1 = (char *) txt1 + len1;
  char *end2 = (char *) txt2 + len2;
  int l;

  *max = 0;
  for (p = (char *) txt1; p < end1; p++) {
    for (q = (char *) txt2; q < end2; q++) {
      for (l = 0; (p + l < end1) && (q + l < end2) && (p[l] == q[l]); l++);
      if (l > *max) {
        *max = l;
        *pos1 = p - txt1;
        *pos2 = q - txt2;
      }
    }
  }
}
/* }}} */


/* {{{ php_similar_char
 */
static int php_similar_char(const char *txt1, int len1, const char *txt2, int len2)
{
  int sum;
  int pos1, pos2, max;

  php_similar_str(txt1, len1, txt2, len2, &pos1, &pos2, &max);

  if ((sum = max)) {
    if (pos1 && pos2) {
      sum += php_similar_char(txt1, pos1,
                  txt2, pos2);
    }
    if ((pos1 + max < len1) && (pos2 + max < len2)) {
      sum += php_similar_char(txt1 + pos1 + max, len1 - pos1 - max,
                  txt2 + pos2 + max, len2 - pos2 - max);
    }
  }

  return sum;
}
/* }}} */

Javascript中的源代码：与 JavaScript
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