| arg | Returns a component of the current Drupal path. |
| bootstrap_hooks | Defines the critical hooks that force modules to always be loaded. |
| bootstrap_invoke_all | Invokes a bootstrap hook in all bootstrap modules that implement it. |
| check_plain | Encodes special characters in a plain-text string for display as HTML. |
| conf_path | Returns the appropriate configuration directory. |
| drupal_add_http_header | Sets an HTTP response header for the current page. |
| drupal_anonymous_user | Generates a default anonymous $user object. |
| drupal_array_merge_deep | Merges multiple arrays, recursively, and returns the merged array. |
| drupal_array_merge_deep_array | Merges multiple arrays, recursively, and returns the merged array. |
| drupal_autoload_class | Confirms that a class is available. |
| drupal_autoload_interface | Confirms that an interface is available. |
| drupal_autoload_trait | Confirms that a trait is available. |
| drupal_base64_encode | Returns a URL-safe, base64 encoded version of the supplied string. |
| drupal_block_denied | Handles denied users. |
| drupal_bootstrap | Ensures Drupal is bootstrapped to the specified phase. |
| drupal_check_memory_limit | Compares the memory required for an operation to the available memory. |
| drupal_clear_opcode_cache | Invalidates a PHP file from any active opcode caches. |
| drupal_environment_initialize | Initializes the PHP environment. |
| drupal_fast_404 | Returns a simple 404 Not Found page. |
| drupal_file_scan_write_cache | Writes the file scan cache to the persistent cache. |
| drupal_generate_test_ua | Generates a user agent string with a HMAC and timestamp for simpletest. |
| drupal_get_bootstrap_phase | Returns the current bootstrap phase for this Drupal process. |
| drupal_get_complete_schema | Gets the whole database schema. |
| drupal_get_filename | Returns and optionally sets the filename for a system resource. |
| drupal_get_hash_salt | Gets a salt useful for hardening against SQL injection. |
| drupal_get_http_header | Gets the HTTP response headers for the current page. |
| drupal_get_messages | Returns all messages that have been set with drupal_set_message(). |
| drupal_get_schema | Gets the schema definition of a table, or the whole database schema. |
| drupal_get_title | Gets the title of the current page. |
| drupal_get_user_timezone | Returns the time zone of the current user. |
| drupal_hash_base64 | Calculates a base-64 encoded, URL-safe sha-256 hash. |
| drupal_hmac_base64 | Calculates a base-64 encoded, URL-safe sha-256 hmac. |
| drupal_installation_attempted | Returns TRUE if a Drupal installation is currently being attempted. |
| drupal_is_cli | Detects whether the current script is running in a command-line environment. |
| drupal_is_denied | Checks to see if an IP address has been blocked. |
| drupal_language_initialize | Initializes all the defined language types. |
| drupal_language_types | Returns a list of the built-in language types. |
| drupal_load | Includes a file with the provided type and name. |
| drupal_maintenance_theme | Enables use of the theme system without requiring database access. |
| drupal_multilingual | Returns TRUE if there is more than one language enabled. |
| drupal_override_server_variables | Sets appropriate server variables needed for command line scripts to work. |
| drupal_page_get_cache | Retrieves the current page from the cache. |
| drupal_page_header | Sets HTTP headers in preparation for a page response. |
| drupal_page_is_cacheable | Determines the cacheability of the current page. |
| drupal_placeholder | Formats text for emphasized display in a placeholder inside a sentence. |
| drupal_random_bytes | Returns a string of highly randomized bytes (over the full 8-bit range). |
| drupal_random_key | Returns a URL-safe, base64 encoded string of highly randomized bytes (over the full 8-bit range). |
| drupal_register_shutdown_function | Registers a function for execution on shutdown. |
| drupal_send_headers | Sends the HTTP response headers that were previously set, adding defaults. |
| drupal_serve_page_from_cache | Sets HTTP headers in preparation for a cached page response. |
| drupal_settings_initialize | Sets the base URL, cookie domain, and session name from configuration. |
| drupal_set_message | Sets a message to display to the user. |
| drupal_set_title | Sets the title of the current page. |
| drupal_static | Provides central static variable storage. |
| drupal_static_reset | Resets one or all centrally stored static variable(s). |
| drupal_unpack | Unserializes and appends elements from a serialized string. |
| drupal_validate_utf8 | Checks whether a string is valid UTF-8. |
| drupal_valid_http_host | Validates that a hostname (for example $_SERVER['HTTP_HOST']) is safe. |
| drupal_valid_test_ua | Returns the test prefix if this is an internal request from SimpleTest. |
| format_string | Formats a string for HTML display by replacing variable placeholders. |
| get_t | Returns the name of the proper localization function. |
| ip_address | Returns the IP address of the client machine. |
| language_default | Returns the default language, as an object, or one of its properties. |
| language_list | Returns a list of installed languages, indexed by the specified key. |
| language_types | Returns an array of the available language types. |
| registry_rebuild | Rescans all enabled modules and rebuilds the registry. |
| registry_update | Updates the registry based on the latest files listed in the database. |
| request_path | Returns the requested URL path of the page being viewed. |
| request_uri | Returns the equivalent of Apache's $_SERVER['REQUEST_URI'] variable. |
| t | Translates a string to the current language or to a given language. |
| timer_read | Reads the current timer value without stopping the timer. |
| timer_start | Starts the timer with the specified name. |
| timer_stop | Stops the timer with the specified name. |
| variable_del | Unsets a persistent variable. |
| variable_get | Returns a persistent variable. |
| variable_initialize | Loads the persistent variable table. |
| variable_set | Sets a persistent variable. |
| watchdog | Logs a system message. |
| watchdog_exception | Logs an exception. |
| _drupal_bootstrap_configuration | Sets up the script environment and loads settings.php. |
| _drupal_bootstrap_database | Initializes the database system and registers autoload functions. |
| _drupal_bootstrap_page_cache | Attempts to serve a page from the cache. |
| _drupal_bootstrap_page_header | Invokes hook_boot(), initializes locking system, and sends HTTP headers. |
| _drupal_bootstrap_variables | Loads system variables and all enabled bootstrap modules. |
| _drupal_error_handler | Provides custom PHP error handling. |
| _drupal_exception_handler | Provides custom PHP exception handling. |
| _drupal_file_scan_cache | Returns the current list of cached file system scan results. |
| _drupal_get_filename_fallback | Performs a cached file system scan as a fallback when searching for a file. |
| _drupal_get_filename_fallback_trigger_error | Triggers a user-level warning for missing or unexpectedly moved files. |
| _drupal_get_filename_perform_file_scan | Performs a file system scan to search for a system resource. |
| _drupal_set_preferred_header_name | Sets the preferred name for the HTTP header. |
| _drupal_shutdown_function | Executes registered shutdown functions. |
| _drupal_trigger_error_with_delayed_logging | Invokes trigger_error() with logging delayed until the end of the request. |
| _registry_check_code | Checks for a resource in the registry. |