Using #required to enforce inputfor Drupal 11 , 10 , 9 , and 8

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11.x , 10.x , 9.x , 8.x

You've used #required => TRUE in nearly every example so far without a dedicated explanation. This lesson makes it explicit: what it actually does, both visually and functionally, and where its automatic validation stops — since #required alone won't catch everything a real field needs validated.

What you'll learn in this lesson

  • What #required does automatically: visual indicator plus server-side check
  • What counts as "empty" for different element types
  • Where #required's job ends and custom validation begins

The two things #required does

$form['email'] = [
  '#type' => 'email',
  '#title' => $this->t('Email address'),
  '#required' => TRUE,
];

Two automatic effects: a visual asterisk added to the label (via CSS, themeable), and a genuine server-side check — if the field is empty on submission, Drupal adds a "field is required" error automatically, before your own validateForm() even runs, without you writing that check yourself.

"Empty" means different things for different element types. For a textfield, empty means an empty string. For checkboxes (plural), empty means every option unchecked. For a select, empty generally means the #empty_option is still selected (which connects directly back to the select lesson's warning about required validation silently not working without one). Know your element's own "empty" definition — #required's automatic check relies on it being correct.

Where #required's job ends

$form['email'] = [
  '#type' => 'email',
  '#title' => $this->t('Email address'),
  '#required' => TRUE, // Catches: field left completely blank.
];
// #type => 'email' ALSO gets automatic format validation (must look
// like an email) — but that's from the element type, not #required.
// #required only ever checks for emptiness, nothing about content shape.

#required answers exactly one question — "was something entered at all?" — and nothing about whether what was entered is actually valid content. A required textfield accepting a phone number still needs its own custom validation (covered in the Form Validation section) to confirm the entered text actually looks like a phone number; #required alone would happily accept "asdf".

Quick check: a required textfield is meant to collect a US ZIP code. A user submits the single character "x". Does #required catch this as invalid? If you said no — #required only checks that something was entered, not that it's a valid ZIP code — you've understood exactly the boundary between #required and custom content validation.

Key takeaways

  • #required => TRUE adds both a visual asterisk and a genuine server-side emptiness check, automatically.
  • "Empty" is defined differently per element type — know your specific element's definition, especially for select and checkboxes.
  • #required only checks presence, never content validity — a required field can still contain garbage that passes #required but fails a real content check.

Coming up next

Required enforces presence. Next, helping a user understand what to actually enter in the first place, with #description.