Last updated February 2, 2013. Created by bekasu on September 18, 2009.
Edited by davidneedham, the1andonlycary, manop. Log in to edit this page.
I am new to module development, and have spent the past month studying this guide and the various Drupal module development books. I have found each very helpful, but have had some difficulty with the database abstraction layer and the Forms API. To test some of the things that I've learned, I curbed my module development to create a rather simple "Test Module". This module makes a simple table to log messages. Those messages can also execute PHP code if they are prefixed by the string "eval:" (so I can test code).
I have attached my code below for each of the three files in hope that someone can benefit from my research (albeit not perfect). The three files are rather standard: test_module.info, test_module.install, and test_module.module. Remember to remove the "?>" from the code to comply with Drupal coding standards:
test_module.info
; $Id$
name = Test Module
description = A Test Module.
core = 6.x
package = "Test"
version = "6.x-0.1-dev"test_module.install
<?php
// $Id$
/**
* Install the test_module module, including it's content (node)
* type.
* @file
*/
/**
* Implementation of hook_install()
*/
function test_module_install() {
drupal_install_schema('test_module');
db_query("DELETE FROM {cache}");
}
/**
* Implementation of hook_uninstall()
*/
function test_module_uninstall() {
drupal_uninstall_schema('test_module');
}
/**
* Implementation of hook_schema()
* @return array of Schema API table definitions.
*/
function test_module_schema() {
$schema['test_module_log'] = array(
'fields' => array(
'id' => array('type' => 'serial', 'size' => 'big', 'unsigned' => TRUE, 'not null' => TRUE,
'description'=> "Log ID"),
'timestamp' => array('type' => 'int', 'not null' => TRUE, 'default' => 0,
'description'=> "Timestamp (Unix Timestamp, which is limited to values above Jan 1, 1970)"),
'message' => array('type' => 'text', 'not null' => FALSE,
'description'=> "Log messages."), //NOTE: On MySQL, text fields cannot have default values.
),
'primary key' => array('id') //Don't put a comma after primary key definition, since doing so will cause database errors.
);
return $schema;
}
?>test_module.module
<?php
// $Id$
/**
* @file
* A Test Module.
*/
/*******************************************************************************
* Hook Functions (Drupal)
******************************************************************************/
/**
* Display help and module information
* @param path which path of the site we're displaying help
* @param arg array that holds the current path as would be returned from arg() function
* @return help text for the path
*/
function test_module_help($path, $arg) {
//$output = '<p>'. t("test_module is a simple module to test functions and pages in Drupal");
// The line above outputs in ALL admin/module pages
switch ($path) {
case "admin/help/test_module":
$output = '<p>'. t("test_module is a simple module to test functions and pages in Drupal") .'</p>';
break;
}
return $output;
} // function test_module_help
/**
* Valid permissions for this module
* @return array An array of valid permissions for the test_module module
*/
function test_module_perm() {
return array('administer test_module', 'access test_module content');
} // function test_module_perm()
/**
* Menu for this module
* @return array An array with this module's settings.
*/
function test_module_menu() {
$items = array();
//Link to the test_module admin page:
$items['admin/settings/test_module'] = array(
'title' => 'Test Module',
'description' => 'Administer Test Module Messages',
'page callback' => 'test_module_message',
'access arguments' => array('administer test_module'),
'type' => MENU_NORMAL_ITEM,
);
return $items;
}
/**
* Test Module Messages
* @return array An array of form data.
*/
function test_module_message() {
$page_content = '';
$page_content .= drupal_get_form('test_module_message_form');
$get_messages = db_query("SELECT * FROM {test_module_log} ORDER BY timestamp DESC");
if ($get_messages !== false) {
$page_content .= "<h2>Test Message Log</h2>";
$row_count = 1;
$id = 0;
while($row = db_fetch_array($get_messages)) {
$page_content .= "<p>";
foreach ($row as $key=>$value) {
if ($key == 'id') $id = $value;
if ($key == 'timestamp') $value = date('F j, Y G:i:s A', $value);
if ($key == 'message') {
if (strpos($value, 'eval:') !== false && $row_count === 1) {
$value = trim(preg_replace('/eval:/', '', $value, 1));
eval($value);
drupal_set_message(t("Executed code:\n").strval($value));
//Once the "eval:" code is evaluated, remove the "eval:" text to avoid executing the code again.
db_query("UPDATE {test_module_log} SET message = '%s' WHERE id = %d", $value, $id);
}
$page_content .= "<br />\n";
}
$page_content .= "<b>".$key."</b> = ".htmlspecialchars(strval($value))." ";
}
$page_contents .= "</p>\n";
$row_count += 1;
}
}
return $page_content;
}
/**
* The callback function (form constructor) that creates the HTML form for test_module_message().
* @return form an array of form data.
*/
function test_module_message_form() {
$form['test_module_message'] = array(
'#type' => 'textarea',
'#title' => t('Message'),
'#default_value' => variable_get('test_module_message', 'Test Message'),
'#cols' => 50,
'#rows' => 5,
'#description' => t("Enter a test message. Begin the message with \"eval:\" to execute PHPcode."),
);
//Submit button:
$form['submit'] = array(
'#type' => 'submit',
'#value' => t('Save Message'),
);
return $form;
}
/**
* Form validation for this module's settings
* @param form an array that contains this module's settings
* @param form_state an array that contains this module's settings
*/
function test_module_message_form_validate($form, &$form_state) {
$test_module_message = $form_state['values']['test_module_message'];
if (isset($test_module_message)) {
if (!is_string($test_module_message) || $test_module_message == '') {
form_set_error('test_module_message', t('Please enter a test message.'));
}
}
}
/**
* Form submission for user data.
* @param form an array that contains user data
* @param form_state an array that contains user data
*/
function test_module_message_form_submit($form, &$form_state) {
$test_message = $form_state['values']['test_module_message'];
$exe_query = db_query("INSERT INTO {test_module_log} (timestamp, message) VALUES(%d, '%s')", time(), $test_message);
$last_id = db_last_insert_id('{test_module_log}','id');
if ($exe_query !== false) {
$msg = 'Added message to log: %id';
$vars = array('%id'=>$last_id);
watchdog('test_module', $msg, $vars, WATCHDOG_INFO);
drupal_set_message(t('Added message to log: ').strval($last_id));
} else {
$msg = 'Could not add message to log: ';
$vars = array();
watchdog('test_module', $msg, $vars, WATCHDOG_ERROR);
drupal_set_message(t('Could not add message to log.'));
}
$form_state['redirect'] = 'admin/settings/test_module';
}
?>
Comments
Problems with test_module
A word of caution:
If you want to practice your coding, type it but don't run it in your drupal site.
I just made that mistake and now I am getting the error:
Fatal error: Unsupported operand types in /home/mavware1/public_html/rickh/includes/common.inc on line 1582
I deleted my files and reinstalled them and I still have the error. I even took out the files for the test module. If anybody has any input on how to fix this problem, please tell me by replying back.
i also had this sort of error
i also had this sort of error lately, i figured out, that i had a ,(comma) instead of a .(dot) somewhere
for example there: drupal_set_message(t("Executed code:\n").strval($value));
Maybe its usefull to show
Maybe its usefull to show your code that contains the bug
We can't smell whats in common.inc on line 1582 ;)
________________________________________________________________________
Insanity: doing the same thing over and over again and expecting different results.
Hi, Have a test drupal
Hi,
Have a test drupal site where u can run all ur tests. With out testing u can never know mistakes and learn from it. so test / try how much u want. what i suggest is that go to DB and see what u entered last and clean it up.
-- Pradeep
Perhaps you use a SQL Reserved Word
Hi
I'd read this useful article a few minutes ago. I found you are using "timestamp" as a key. It appears as SQL reserved word (mysql "permits" it, but ¿your driver?) see the ANSI SQL 2003 link at "List of Sql Reserved Words" (is a Drupal Site's page http://drupal.org/node/141051). There you'll find TIMESTAMP.
It seems as thats what was wrong.
This tutorial is very helpful
This tutorial is very helpful to start learning Drupal-API . Thank you.
There is a little bug in test_module_help function to see module description in Help menu:
case 'admin/help/test_module':must be
case 'admin/help#test_module':Very Usefual,cool,this
Very Usefual,cool,this example make me understand the normal module develop
test module
I installed and enabled this but I dont know how to test it. how do I make it run? what url?
There are some issues with drupal_install_schema()
Hi.
Thank you for your help. I understood wath I'm needing.
Reading around drupal documents I found some issues reporting drupal_install() runs drupall_install_schema() so your table is found when you try to create it. see "on drupal_install_schema search"
I suggest to write a couple of code lines to avoid dificulties:
$testquery = "SHOW TABLES";$query_result = db_query($testquery);
... lines to test if your table exists ...
// $not_exists = true | false as result
if ($not_exists) {
// call the function
drupal_install_schema('your_module_table');
}
Notes:
Hope it helps