How can HTML validation affect PHP form functionality?

When HTML validation is enabled on a form, it can prevent the form from being submitted if any of the fields do not meet the specified validation criteria. This can affect PHP form functionality as the PHP code will not be executed if the form submission is blocked by HTML validation. To solve this issue, you can disable HTML validation on the form by setting the "novalidate" attribute on the form tag.

<form action="submit.php" method="post" novalidate>
  <!-- Form fields go here -->
  <input type="submit" value="Submit">
</form>