.. efun:: int strstr(string str, string str2)
  int strstr(string str, string str2, int pos)

  Returns the index of :arg:`str2` in :arg:`str`, searching from position :arg:`pos` on.

  The returned index is relative to the beginning of the string. If :arg:`str2` is not found in :arg:`str`, -1 is returned.

  If :arg:`pos` is negative, it designates the start position relative to the end of the string (the search will still proceed towards the end of the string).

  .. seealso:: :efun:`strrstr`, :efun:`strlen`, :efun:`sscanf`, :efun:`sprintf`, :efun:`explode`