Drupal 7 Module Development

Installation Profiles
There are some tasks which need to be run after a certain point in the process on
every page load. An example of this is in the default install tasks. The installer
initializes with a low-level Drupal bootstrap enabling very base level functionality.
After the modules have been installed but before the site configuration part of the
process, there is a point when the installer can do a full Drupal bootstrap with all the
functionality of all the enabled modules. Once the installer reaches this point it runs
a task on all subsequent page loads to perform a full Drupal bootstrap. The definition
for this task looks like the following:
$tasks = array(
...
'install_bootstrap_full' => array(
'run' => INSTALL_TASK_RUN_IF_REACHED,
),
...
);
By setting run to INSTALL_TASK_RUN_IF_REACHED, the function install_bootstrap_
full() is run on every page load after it is encountered in the install tasks.
Altering tasks
The installer provides a method to alter tasks in the installer. Where
hook_install_tasks() provides a method to add tasks at the end of the install
process, hook_install_tasks_alter() provides access to all the tasks in the
installer (including the default tasks provided by the installer). This allows a profile
to insert tasks earlier in the install process or alter the default tasks.
Tasks performed before the install_bootstrap_full() task, which
is before the modules are installed, only have access to a very base level of
Drupal configuration, with access to the system module, user module, the
PHP settings, and a site's settings.php file.
Let's look at an example of altering tasks before the modules are installed; only the
base level system is available, which means your installation profile is not yet able to
call hook_form_alter or hook_form_FORM_ID_alter. In this case we want to alter
the step where the database is set up to add some additional instructions.
/**
* Implements hook_install_tasks_alter().
*/
function store_install_tasks_alter(&$tasks, &$install_state) {
$tasks['install_settings_form']['function'] = 'store_database_
settings_form';
}
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