FormBuilderEntries::exportCSV() method      
Works like find() except that it exports and sends a CSV file to output
This function also halts execution of the request after the CSV has been delivered
Note: to set the content-type header do the following in your /site/config.php file:
$config->contentTypes('csv', 'text/csv');
Replace the 'text/csv' above with the content-type header you want to use. Note that
the default used in this method is 'application/force-download'.
Usage
// basic usage
$entries->exportCSV(FormBuilderForm $form, string $selectorString);
// usage with all arguments
$entries->exportCSV(FormBuilderForm $form, string $selectorString, array $options = []);Arguments
| Name | Type(s) | Description | 
|---|---|---|
| $form | FormBuilderForm | Specifying the form here is required, you can use $entries->getForm() if you'd like. | 
| $selectorString | string | Selector string to match extries to export. | 
| $options(optional) | array | Options to modify behavior: 
 | 
Hooking $entries→exportCSV(…)
You can add your own hook events that are executed either before or after the $entries->exportCSV(…) method is executed. Examples of both are included below. A good place for hook code such as this is in your /site/ready.php file.
Hooking before
The 'before' hooks are called immediately before each $entries->exportCSV(…) method call is executed. This type of hook is especially useful for modifying arguments before they are sent to the method.
$this->addHookBefore('FormBuilderEntries::exportCSV', function(HookEvent $event) {
  // Get the object the event occurred on, if needed
  $FormBuilderEntries = $event->object;
  // Get values of arguments sent to hook (and optionally modify them)
  $form = $event->arguments(0);
  $selectorString = $event->arguments(1);
  $options = $event->arguments(2);
  /* Your code here, perhaps modifying arguments */
  // Populate back arguments (if you have modified them)
  $event->arguments(0, $form);
  $event->arguments(1, $selectorString);
  $event->arguments(2, $options);
});      Hooking after
The 'after' hooks are called immediately after each $entries->exportCSV(…) method call is executed. This type of hook is especially useful for modifying the value that was returned by the method call.
$this->addHookAfter('FormBuilderEntries::exportCSV', function(HookEvent $event) {
  // Get the object the event occurred on, if needed
  $FormBuilderEntries = $event->object;
  // An 'after' hook can retrieve and/or modify the return value
  $return = $event->return;
  // Get values of arguments sent to hook (if needed)
  $form = $event->arguments(0);
  $selectorString = $event->arguments(1);
  $options = $event->arguments(2);
  /* Your code here, perhaps modifying the return value */
  // Populate back return value, if you have modified it
  $event->return = $return;
});      $entries methods and properties
API reference based on ProcessWire core version 3.0.252