Displaying Validation Errors

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

The Four 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.

<h1><?= $headline ?></h1>
<?= validation_errors() ?>

<?php
echo form_open($form_location);
echo form_label('Email');
echo form_input('email', $email);
echo form_label('Password');
echo form_password('password');
echo form_submit('submit', 'Save');
echo form_close();
?>

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

Customising Output

• Wrap each error:
  View File

  <?= validation_errors('<div class="error">', '</div>') ?>

• Set global defaults:
  PHP

  define('ERROR_OPEN', '<div class="alert alert-danger">');
  define('ERROR_CLOSE', '</div>');

• Wrap the full block:
  View File

  <div class="error-container">
    <?= validation_errors() ?>
  </div>

Method 2: Scoped Errors (Form-Specific)

On pages with more than one form, give each form a form_name and render only that form's errors with the FORM- prefix. This prevents one form's errors from appearing under a different form.

<?php
echo form_open($login_location, ['form_name' => 'login']);
echo form_label('Email');
echo form_input('email', $email);
echo form_label('Password');
echo form_password('password');
echo form_submit('submit', 'Log In');
echo validation_errors('FORM-login'); // Login form's errors only
echo form_close();

// Second form on the same page...
echo form_open($contact_location, ['form_name' => 'contact']);
// ... contact fields ...
echo validation_errors('FORM-contact'); // Contact form's errors only
echo form_close();
?>

Scoped rendering uses the default error wrappers. For custom wrappers plus scoping, use the position-3 spelling:

<?= validation_errors('</p>', '<p>', 'login') ?>

Method 3: 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.

<?php
echo form_open($form_location);

echo form_label('Email Address');
echo validation_errors('email');
echo form_input('email', $email);

echo form_label('Password');
echo validation_errors('password');
echo form_password('password');

echo form_submit('submit', 'Register');
echo form_close();
?>

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

Method 4: JSON Errors (APIs and AJAX)

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

public function api_create(): void {
    $this->validation->set_rules('email', 'email address', 'required|valid_email');
    $this->validation->set_rules('password', 'password', 'required|min_length[8]');
 
    if ($this->validation->run() === false) {
        validation_errors(422);
    }
    
    echo json_encode(['success' => true]);
}

Example JSON response:

[
  {
    "field": "email",
    "messages": ["The email address field is required."]
  }
]

Automatic Error Highlighting

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

<?php
echo form_open($form_location, ['class' => 'highlight-errors']);
echo form_label('Email');
echo form_input('email', $email);
echo form_label('Password');
echo form_password('password');
echo form_submit('submit', 'Login');
echo form_close();
?>

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
• Multi-form pages: Use scoped errors
• APIs: Use JSON responses

Session Behaviour (Advanced)