#drupal Form and Block Render to display site alert message. Drupal 7

Form and Block Render Example

<?php

/**
 * @file
 * Create form for alert message entry and render a block with message if message is not empty. Blocked place in header in this example with custom CSS.
 */

/**
 * Implements hook_menu().
 */
function example_alert_blocks_menu() {
  $items = array();

  $items['admin/alert-message'] = array(
    'title' => 'Configure Alert Message',
    'description' => '',
    'position' => 'left',
    'weight' => 100,
    'page callback' => 'drupal_get_form',
    'page arguments' => array('example_alert_blocks_config'),
    'access arguments' => array('access content overview'),
  );


  return $items;
}

function example_alert_blocks_config() {
  $form = array();

  $form['example_alert_message'] = array(
    '#type' => 'textfield',
    '#title' => t('Alert Message'),
    '#default_value' => variable_get('example_alert_message', ''),
    '#maxlength' => 200,
    '#size' => 200,
    '#description' => t('Leave blank for none.'),
  );

  $form = system_settings_form($form);
  $form['#submit'][] = 'example_alert_blocks_cc';
  return $form;
}

function example_alert_blocks_cc() {
  drupal_flush_all_caches();
  drupal_set_message(t('Caches cleared.'));
}

/**
 * Implements hook_block_info().
 */
function example_alert_blocks_block_info() {
  $blocks = array();
  $blocks['example_alert_block'] = array('info' => t('Alert Notification'), 'cache' => DRUPAL_NO_CACHE);
  return $blocks;
}

/**
 * Implements hook_block_view().
 */
function example_alert_blocks_block_view($block_name = '') {

  if ($block_name == 'example_alert_block') {
    $alert_message = variable_get('example_alert_message', '');
    if (empty($alert_message)) {
      $block = array();
    }
    else {
      $block = array(
        'subject' => t('<NONE>'),
        'content' => '<p>' . variable_get('example_alert_message', '') . '</p>',
      );
    }
    return $block;
  }
}