strrchr with needle with multiple characters

I was today old when I discovered the big difference between strchr and strrchr in the way they handle needle with multiple characters. It's explained in the doc https://www.php.net/manual/en/function.strrchr.php - If needle contains more than one character, only the first is used. This behavior is different from that of strstr() <https://www.php.net/manual/en/function.strstr.php>. You can see an example https://3v4l.org/7j5ab I feel like this behavior has no benefit (if I want to look for the first character, I can pass substr($needle, 0, 1) instead) and is just error-prone. Is there a reason for such behavior ? Would it be easy to change it (I have no knowledge at all in C and in the existing PHP code) ?