strlen( $s)
strpos( $haystack, $needle, $offset)
strrpos( $haystack, $needle, $offset)
substr( $string, $start, $length = PHP_INT_MAX)
stripos( $s, $needle, $offset)
stristr( $s, $needle, $part = false)
strrchr( $s, $needle, $part = false)
strripos( $s, $needle, $offset)
strstr( $s, $needle, $part = false)