Get all unused fields via API

Problem

You want to be a good housekeeper and do some cleanup on a complex site with many fields and templates. After years of working on the project you have lost track of which fields are actually used by any templates.

Solution

Don’t worry and get all unused fields via API. The Field class has a method getTemplates() that we can use. This method returns all templates that have this field assigned. If the count of getTemplates() is 0 then we can be sure that this field is not used by any template.

$danglingFields = new WireArray();
// Iterate through all fields in the system
foreach ($fields as $f) {
    // Check if the field is not used by any template
    if ($f->getTemplates()->count === 0) {
        // If the field is unused, add it to the $danglingFields WireArray
        $danglingFields->add($fields->get($f));
    }
}
// now $danglingFields is a WireArray of Field objects.
// Do with it as you please.
// You could delete all unused fields:
// foreach($danglingFields as $f) $fields->delete($f);
// But caution. They will be gone for good.
//You better make a DB backup before doing this.