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:

  • "SystemEnvironmentBuilder" = \TYPO3\CMS\Core\Core\SystemEnvironmentBuilder

  • "Bootstrap" = \TYPO3\CMS\Core\Core\Bootstrap

Check SystemEnvironmentBuilder::defineBaseConstants() 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

Filetypes

Different types of files 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

FILETYPE_UNKNOWN

0

Unknown

FILETYPE_TEXT

1

Any kind of text

FILETYPE_IMAGE

2

Any kind of image

FILETYPE_AUDIO

3

Any kind of audio

FILETYPE_VIDEO

4

Any kind of video

FILETYPE_APPLICATION

5

Any kind of application

HTTP status codes

The different status codes available are defined in TYPO3\CMS\Core\Utility\HttpUtility. These constants are defined as documented in https://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml