Функция PHP mb_substr_count

int mb_substr_count ( string haystack, string needle [, string encoding] )

mb_substr_count returns the number of times the needle substring occurs in the haystack string.

encoding specifies the encoding for needle and haystack. If omitted, internal character encoding is used.

Пример использования mb_substr_count:

  <?php
   echo mb_substr_count("This is a test", "is"); // prints out 2
?>

See also substr_count, mb_strpos, mb_substr.