function_usable($function_name)

get_mimes()

mb_substr($str, $start[, $length = NULL[, $encoding = NULL]])

remove_invisible_characters($str[, $url_encoded = TRUE])

array_replace_recursive(array $array1[, ...])

array_column(array $array, $column_key[, $index_key = NULL])

html_escape($var)

config_item($key)

log_message($level, $message)

set_status_header($code[, $text = ''])