Basics of Debugging in Drupal
Evgeniy Melnikov
www.angarsky.ru
@angarsky
Developer's problems
- You don't understand how Drupal core works?
- Your site shows a white screen?
- You can't fix a bug within a several hours?
- You have to work on a site with a lot of custom code that was developed by another developer?
- Your site crashes after module updates?
- ...
Calm down and start to analyze
- Check Drupal logs (admin/reports/dblog)
- Check server logs
- Detect a problematic part of code
- Developer tools will help you to solve a problem!
Devel module
- A simple tool for Drupal debugging
- Allows to display variables of functions
- Allows to display a compiled SQL query
- Allows to prints a function call stack
- Provides an information about theme registry, current menu item, user's session
- Provides an interface to view and edit Drupal variables
- Provides a quick links to flush a cache, run a cron, rebuild menus
https://www.drupal.org/project/devel
Devel module
Function dsm()
https://www.drupal.org/project/devel
Devel module
Function dpq()
https://www.drupal.org/project/devel
/**
* Implements hook_preprocess_HOOK().
*/
function bootstrap_mel_preprocess_page(&$vars) {
$d = db_select('users', 'u')
->fields('u', array('name', 'created'))
->condition('u.status', 1);
dpq($d);
}
Devel module
Function ddebug_backtrace()
https://www.drupal.org/project/devel
Haked! module
- This module scans the currently installed Drupal, contributed modules and themes, re-downloads them and determines if they have been changed
- Install the Diff module to see the exact lines that have changed
https://www.drupal.org/project/hacked
Drupal function watchdog()
- A Drupal function out of box
- Writes a specified data to Drupal logs
/**
* Function definition.
*/
function watchdog($type, $message, $variables = array(), $severity = WATCHDOG_NOTICE, $link = NULL) {}
// How to use this function.
watchdog('my_module', 'Data to show - @data.', array('@data' => $some_data), WATCHDOG_DEBUG);
- See the data in Drupal logs (admin/reports/dblog)
- Note: arrays should be serialized before sending in watchdog()
Preview settings of the Views module
- Show the SQL query
- Show performance statistics
- Show other queries run during render during live preview
GIT
GIT
- Possibility to go back to a last stable version of code
- Prevents occasional errors of developer
- History of code updates
- Possibility to create an experimental code
Integrated Development Environment (IDE)
Integrated Development Environment (IDE)
- Loads a whole project with all files, functions, classes
- Search and autocomplete for functions
- Highlighting of variables, functions, code errors
- Indents and formatting
- References for functions, classes, methods, variables
- Integration with Git (or another VCS)
Debugger
XDebug — a PHP extension for powerful debugging. It supports stack and function traces, profiling information and memory allocation and script execution analysis.
Questions?
Basics of Debugging in Drupal
Evgeniy Melnikov
www.angarsky.ru
@angarsky
DS - Basics of Debugging in Drupal
By Semen Angarsky
