Function stripos in PHP4
According to the document of PHP official website, http://php.net/stripos stripos (PHP 5) stripos — Find the position of the first occurrence of a case-insensitive substring…
mbstring provides multibyte specific string functions that help you deal with multibyte encodings in PHP. In addition to that, mbstring handles character encoding conversion between the possible encoding pairs. mbstring is designed to handle Unicode-based encodings such as UTF-8 and UCS-2 and many single-byte encodings for convenience. Read more about PHP: function mb_str_split …
According to the document of PHP official website, http://php.net/manual/en/function.str-split.php
str_split
(PHP 5) str_split — Convert a string to an array