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Data Compiling

This is the first step of FormEngine. The data compiling creates an array containing all data the rendering needs to come up with a result.

A basic call looks like this:

$formDataGroup = GeneralUtility::makeInstance(TcaDatabaseRecord::class);
$formDataCompiler = GeneralUtility::makeInstance(FormDataCompiler::class, $formDataGroup);
$formDataCompilerInput = [
   'tableName' => $table,
   'vanillaUid' => (int)$theUid,
   'command' => $command,
$formData = $formDataCompiler->compile($formDataCompilerInput);

The above code is a simplified version of the relevant part of the EditDocumentController. This controller knows by its GET or POST parameters which record ("vanillaUid") of which specific table ("tableName") should be edited (command="edit") or created (command="new"), and sets this as init data to the DataCompiler. The controller also knows that it should render a full database record and not only parts of it, so it uses the TcaDatabaseRecord data provider group to trigger all data providers relevant for this case. By calling ->compile() on this data group, all providers configured for this group are called after each other, and formData ends up with a huge array of data record details.

So, what happens here in detail?

  • Variable $formDataCompilerInput maps input values to keys specified by FormDataCompiler as "init" data.

  • FormDataCompiler returns a unified array of data. This array is enriched by single data providers.

  • A data provider group is a list of single data providers for a specific scope and enriches the array with information.

  • Each data provider is called by the DataGroup to add or change data in the array.

The variable $formData roughly consists of this data after calling $formDataCompiler->compile():

  • A validated and initialized list of current database row field variables.

  • A processed version of $TCA['givenTable'] containing only those column fields a current user has access to.

  • A processed list of items for single fields like select and group types.

  • A list of relevant localizations.

  • Information of expanded inline record details if needed.

  • Resolved flex form data structures and data.

  • A lot more

Basic goal of this step is to create an array in a specified format with all data needed by the render-part of FormEngine. A controller initializes this with init data, and then lets single data providers fetch additional data and write it to the main array. The deal is here that the data within that array is not structured in an arbitrary way, and each single data provider only adds data the render part of FormEngine understands and needs later. This is why the main array keys are restricted: The main array is initialized by FormDataCompiler, and each DataProvider can only add data to sub-parts of that array.


The main data array is prepared by FormDataCompiler, each key is well documented in this class. To find out which data is expected to reside in this array, those comments are worth a look.


It may happen in future versions of FormEngine (core version 9+) that the responsibility for the main structure and integrity of the data array will be moved away from FormDataCompiler into the single FormDataGroup class. This may even make the FormDataCompiler obsolete in total.

Data Groups and Providers

So we have this empty data array, pre-set with data by a controller and then initialized by FormDataCompiler, which in turn hands over the data array to a specific FormDataGroup. What are these data providers now? Data providers are single classes that add or change data within the data array. They are called in a chain after each other. A FormDataGroup has the responsibility to find out, which specific single data providers should be used, and calls them in a specific order.

Data compiling by multiple providers

Why do we need this?

  • Which data providers are relevant depends on the specific scope: For instance, if editing a full database based record, one provider fetches the according row from the database and initializes $data['databaseRow'] . But if flex form data is calculated, the flex form values are fetched from table fields directly. So, while the DatabaseEditRow data provider is needed in the first case, it's not needed or even counter productive in the second case. The FormDataGroup's are used to manage providers for specific scopes.

  • FormDataGroups know which providers should be used in a specific scope. They usually fetch a list of providers from some global configuration array. Extensions can add own providers to this configuration array for further data munging.

  • Single data providers have dependencies to each other and must be executed in a specific order. For Instance, the PageTsConfig of a record can only be determined, if the rootline of a record has been determined, which can only happen after the pid of a given record has been consolidated, which relies on the record being fetched from the database. This makes data providers a linked list and it is the task of a FormDataGroup to manage the correct order.

Main data groups:


List of providers used if rendering a database based record.


List of data providers used to prepare flex form data and flex form section container data.


List of data providers used to prepare placeholder values for type=input and type=text fields.


List of data providers used to prepare data needed if an inline record is opened from within an ajax call.


A special data group that can be initialized with a list of to-execute data providers directly. In contrast to the others, it does not resort the data provider list by its dependencies and does not fetch the list of data providers from a global config. Used in the core at a couple of places, where a small number of data providers should be called right away without being extensible.


It is a good idea to set a breakpoint at the form data result returned by the DataCompiler and to have a look at the data array to get an idea of what this array contains after compiling.

Let's have a closer look at the data providers. The main TcaDatabaseRecord group consists mostly of three parts:

Main record data and dependencies:

  • Fetch record from DB or initialize a new row depending on $data['command'] being "new" or "edit", set row as $data['databaseRow']

  • Add userTs and pageTsConfig to data array

  • Add table TCA as $data['processedTca']

  • Determine record type value

  • Fetch record translations and other details and add to data array

Single field processing:

  • Process values and items of simple types like type=input, type=radio, type=check and so on. Validate their databaseRow values and validate and sanitize their processedTca settings.

  • Process more complex types that may have relations to other tables like type=group and type=select, set possible selectable items in $data['processedTca'] of the according fields, sanitize their TCA settings.

  • Process type=inline and type=flex fields and prepare their child fields by using new instances of FormDataCompiler and adding their results to $data['processedTca'].

Post process after single field values are prepared:

  • Execute display conditions and remove fields from $data['processedTca'] that shouldn't be shown.

  • Determine main record title and set as $data['recordTitle']

Extending Data Groups With Own Providers

The base set of DataProviders for all DataGroups is defined within typo3/sysext/core/Configuration/DefaultConfiguration.php in section ['SYS']['formEngine']['formDataGroup'], and ends up in variable $GLOBALS['TYPO3_CONF_VARS'] after core bootstrap. The provider list can be read top-down, so the DependencyOrderingService typically does not resort this list to a different order.

Adding an own provider to this list means adding an array key to that array having a specification where the new data provider should be added in the list. This is done by the arrays depends and before.

As an example, the extension "news" uses an own data provider to do additional flex form data structure preparation. The core internal flex preparation is already split into two providers: TcaFlexPrepare determines the data structure and parses it, TcaFlexProcess uses the prepared data structure, processes values and applies defaults if needed. The data provider from the extension "news" hooks in between these two to add some own preparation stuff. The registration happens with this code in ext_localconf.php:

// Modify flexform fields since core 8.5 via formEngine: Inject a data provider
// between TcaFlexPrepare and TcaFlexProcess
if (\TYPO3\CMS\Core\Utility\VersionNumberUtility::convertVersionNumberToInteger(TYPO3_version) >= 8005000) {
    [\GeorgRinger\News\Backend\FormDataProvider\NewsFlexFormManipulation::class] = [
        'depends' => [
        'before' => [

This is pretty powerful since it allows extensions to hook in additional stuff at any point of the processing chain, and it does not depend on the load order of extensions.


  • It is not easily possible to "kick out" an existing provider if other providers have dependencies to them - which is usually the case.

  • It is not easily possible to substitute an existing provider with an own one.


It may happen that the core splits or deletes the one or the other DataProvider in the future. If then an extension has a dependency to a removed provider, the DependencyOrderingService, which takes care of the sorting, throws an exception. There is currently no good solution in the core on how to mitigate this issue.


Data providers in general should not know about renderType, but only about type. Their goal is to prepare and sanitize data independent of a specific renderType. At the moment, the core data provider just has one or two places, where specific renderType's are taken into account to process data, and those show that these areas are a technical debt that should be changed.

Adding Data to Data Array

Most custom data providers change or add existing data within the main data array. A typical use case is an additional record initialization for specific fields in $data['databaseRow'] or additional items somewhere within $data['processedTca']. The main data array is documented in FormDataCompiler->initializeResultArray().

Sometimes, own DataProviders need to add additional data that does not fit into existing places. In those cases they can add stuff to $data['customData']. This key is not filled with data by core DataProviders and serves as a place for extensions to add things. Those data components can be used in own code parts of the rendering later. It is advisable to prefix own data in $data['customData'] with some unique key (for instance the extension name) to not collide with other data that a different extension may add.

Disable Single FormEngine Data Provider

Single data providers used in the FormEngine data compilation step can be disabled to allow extension authors to substitute existing data providers with their solutions.

As an example, if editing a full database record, the default TcaCheckboxItems could be removed by setting disabled in the tcaDatabaseRecord group in an extension's ext_localconf.php file:

[\TYPO3\CMS\Backend\Form\FormDataProvider\TcaCheckboxItems::class]['disabled'] = true;

Extension authors can then add an own data provider, which depends on the disabled one and is configured as before the next one. Therefore effectively substituting single providers with their solution if needed.