Constants

Constants in TYPO3 define paths and database information. These values are global and cannot be changed. Constants are defined at various points during the bootstrap sequence.

To make the information below a bit more compact, namespaces were left out. Here are the fully qualified class names referred to below:

Check \TYPO3\CMS\Core\Core\SystemEnvironmentBuilder::defineBaseConstants() method for more constants.

Paths

TYPO3_mainDir

Deprecated since version 12.0: Accessing the constant will stop working in TYPO3 v13.

It is recommended to use the TYPO3\CMS\Core\Routing\BackendEntryPointResolver class when needing to direct to the TYPO3 Backend.

This is the directory of the backend administration for the sites of this TYPO3 installation. Hardcoded to typo3/. Must be a subdirectory to the website.

Defined in:

SystemEnvironmentBuilder::defineBaseConstants()

Available in Frontend:

Yes

Security-related constant

FILE_DENY_PATTERN_DEFAULT

Default value of $GLOBALS['TYPO3_CONF_VARS']['BE']['fileDenyPattern'].

Defined in:

\TYPO3\CMS\Core\Resource\Security\FileNameValidator::FILE_DENY_PATTERN_DEFAULT

Example:

\\.(php[3-8]?|phpsh|phtml|pht|phar|shtml|cgi)(\\..*)?$|\\.pl$|^\\.htaccess$

Available in frontend:

Yes

TYPO3

TYPO3 still has some extension PHP script files executed in global context without class or callable encapsulation, namely ext_localconf.php, ext_tables.php and files within Configuration/TCA/Overrides/. When those files are located within the public document root of an instance and called via HTTP directly, they may error out and render error messages. This can be a security risk. To prevent this, those files must have a security gate as first line:

<?php

defined('TYPO3') or die();

// ... your code

It is defined to true in early TYPO3 bootstrap.

See also

• ext_localconf.php

• ext_tables.php

• Configuration/TCA/Overrides/

File types

Different types of file constants are defined in \TYPO3\CMS\Core\Resource\AbstractFile. These constants are available for different groups of files as documented in https://www.iana.org/assignments/media-types/media-types.xhtml

These file types are assigned to all FAL resources. They can, for example, be used in Fluid to decide how to render different types of files.

Constant	Value	Description
AbstractFile::FILETYPE_UNKNOWN	0	Unknown
AbstractFile::FILETYPE_TEXT	1	Any kind of text
AbstractFile::FILETYPE_IMAGE	2	Any kind of image
AbstractFile::FILETYPE_AUDIO	3	Any kind of audio
AbstractFile::FILETYPE_VIDEO	4	Any kind of video
AbstractFile::FILETYPE_APPLICATION	5	Any kind of application

HTTP status codes

The different status codes available are defined in EXT:core/Classes/Utility/HttpUtility.php. These constants are defined as documented in https://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml