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Debug-technics.md

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  • mix of print_r and d custom function that add a die and other stuff The behavior is different than dpm because it's printed on the script page and not on the following one. the d() function is here https://gist.github.com/4060502

Lister tous les hook appelé par drupal dans drupal 7 includes/modules.inc

print "<pre>";
print_r(debug_backtrace());
print "</pre>";

To print the calling function without the arguments passsed from function to function

print "<pre>";
print_r(debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS));
print "</pre>";
  • Debug the user_access function
    Display the permission string return FALSE
if (!$perm[$account->uid][$string]){print_r($string . '<br>');}

  • How to know a template is being used Just place a d('are you in used'); If it's in used, a white screen will show with this message

  • How to debug with dpml in a context where you can't
    You are debugging an ajax called page, and the dpm is not accessible, per aps because the message area isn't called. Simply refresh the browser in the page you want to debug, then refresh it in another page. As dpm show in the next page request, it'll show there !!!

  • Recursion in not the end dpm
    When using devel, it occure that a element is shown as recursion. To see what's inside, make an other dpm with only this sub element key For exemple if writing dpm($form) you see $form['view'] show recursion

you can write write dpm($form['view']); to see what's inside

  • Difference between debuging function in php var_dump , var_export , print_r
    http://stackoverflow.com/questions/5039431/difference-between-var-dump-var-export-print-r

  • Output all defined variables
    When in a template and we don't know which variables are defined in this context, we can use a php function get_defined_vars http://php.net/manual/en/function.get-defined-vars.php

  • debug an auto complete
    An autocomplete don't retrieve node's title we expected, just change it to select list to see what's are available choices

  • debug the creation of a db schema
    The schema is installed only for the first installation of a module. So If it does'nt pass the first time, it's necessary to disable + install the module And then reinstall it. A trick could be to call drupal_install_schema function from a hook init so you can debug database installation without doing those boring steps

  • know that a function pass by there
    put small message output with d() function that break execution https://gist.github.com/4060502

  • Debug the SQL query drupal is actually doing after all the abastraction layers has been passed
    Set the devel module to display the queries and find yours Easier

$result = db_query("SELECT 'name' from {taxonomy_term_data} WHERE 'tid' IN (" . implode(',' , $tid) . ")");
dpm($result);
// Will show
SELECT 'name' from taxonomy_term_data WHERE 'tid' IN (8,1635,105654,3988,170)
  • Debugging the SQL Query
    To examine the SQL query that the query object will build at a particular point in its lifecycle, call its __toString() method:
<?php
  print_r($query->__toString());
?>