Displaying Validation Errors

When validation fails, Trongate stores errors in $_SESSION['form_submission_errors'] and provides three simple ways to display them.

The Three Display Methods

Method 1: General Errors (Display All)

Use validation_errors() with no arguments to display all validation errors at once, typically at the top of your form.

This approach is ideal for short forms where a single error summary is sufficient.

Customising Output

• Wrap each error:
  <?= validation_errors('<div class="error">', '</div>') ?>
• Set global defaults:
  define('ERROR_OPEN', '<div class="alert alert-danger">'); define('ERROR_CLOSE', '</div>');
• Wrap the full block:
  <div class="error-container"> <?= validation_errors() ?> </div>

Method 2: Inline Errors (Field-Specific)

Pass a field name to display errors next to the relevant input. This provides a more precise and user-friendly experience.

This method is ideal for longer or more complex forms where users benefit from seeing exactly where problems occur.

Method 3: JSON Errors (APIs and AJAX)

Pass an HTTP status code (400–499) to return validation errors as JSON and immediately terminate execution.

Example JSON response:

Automatic Error Highlighting

Add the highlight-errors class to your form to automatically highlight fields that failed validation.

When validation errors exist, form_close() injects JavaScript that applies the form-field-validation-error class to affected fields.

Choosing the Right Approach

• Simple forms: Use general errors
• Complex forms: Use inline errors
• APIs: Use JSON responses

Session Behaviour (Advanced)