init ( )
internal_encoding ( $encoding = NULL )
length ( $str, $enc )
stripos ( $str, $needle )
stristr ( $str, $needle, $part = false )
strpos ( $str, $needle )
strrchr ( $str, $needle, $part = false )
strripos ( $str, $needle )
strrpos ( $str, $needle )
strstr ( $str, $needle, $part = false )
substr ( $str, $start, $end = NULL )
substr_count ( $str, $needle )
tolower ( $str )
toupper ( $str )