Creating hooks

You are encouraged to create hooks in your extensions if they seem meaningful. Typically someone would request a hook somewhere. Before you implement it, consider if it is the right place to put it etc. On the one hand we want to have many hooks but not more than needed. Redundant hooks or hooks which are implemented in the wrong context is just confusing. So put a little thought into it first, but be generous.

There are two main methods of calling a user defined function in TYPO3.

  • \TYPO3\CMS\Core\Utility\GeneralUtility::callUserFunction() - The classic way. Takes a file/class/method reference as value and calls that function. The argument list is fixed to a parameter array and a parent object. So this is the limitation. The freedom is that the reference defines the function name to call. This method is mostly useful for small-scale hooks in the sources.
  • \TYPO3\CMS\Core\Utility\GeneralUtility::getUserObject() - Create an object from a user defined file/class. The method called in the object is fixed by the hook, so this is the non-flexible part. But it is cleaner in other ways, in particular that you can even call many methods in the object and you can pass an arbitrary argument list which makes the API more beautiful. You can also define the objects to be singletons, instantiated only once in the global scope.

Here follows some examples.

Using TYPO3CMSCoreUtilityGeneralUtility::getUserObj()

    // Hook for pre-processing of the content for formmails:
if (is_array($this->TYPO3_CONF_VARS['SC_OPTIONS']['tslib/class.tslib_fe.php']['sendFormmail-PreProcClass'])) {
    foreach($this->TYPO3_CONF_VARS['SC_OPTIONS']['tslib/class.tslib_fe.php']['sendFormmail-PreProcClass'] as $_classRef) {
        $_procObj = \TYPO3\CMS\Core\Utility\GeneralUtility::getUserObj($_classRef);
        $EMAIL_VARS = $_procObj->sendFormmail_preProcessVariables($EMAIL_VARS, $this);

Using with TYPO3CMSCoreUtilityGeneralUtility::callUserFunction()

    // Call post-processing function for constructor:
if (is_array($this->TYPO3_CONF_VARS['SC_OPTIONS']['tslib/class.tslib_fe.php']['tslib_fe-PostProc'])) {
    $_params = array('pObj' => &$this);
    foreach($this->TYPO3_CONF_VARS['SC_OPTIONS']['tslib/class.tslib_fe.php']['tslib_fe-PostProc'] as $_funcRef) {
        \TYPO3\CMS\Core\Utility\GeneralUtility::callUserFunction($_funcRef,$_params, $this);