Controller method does not get data passed through jQuery.ajax()

Question

I am developing a Joomla component. In javascript I use jQuery.ajax() for making a (php) controller method put data (from javascript) into the database. However, after installing the component on one Joomla site, it works, but on another site the data passed through jQuery.ajax() is not obtained by JInput::get().

The (simplified) ajax request is as follows:

jQuery.ajax( {
  'type': 'POST',
  'url': 'index.php?option=com_example&task=examplecontroller.handleAjaxRequest',
  'data': { 'ajaxData': 'test' },
  'success': function( ajaxResult ) {
    alert( ajaxResult );
  }
} );

The (simplified) controller method:

public function handleAjaxRequest()
{
  $app = JFactory::getApplication();
  $input = $app->input;
  echo $input->get( "ajaxData", "defaultValue", "string" );
  $app->close();
}

On one of my sites, an alert with text 'test' is shown as expected. But on the other site, an alert with text 'defaultValue' is shown, indicating that JInput::get() did not find data item 'ajaxData' and used the default value provided in its second parameter.

Both sites are installed on the same domain, each on a different subdomain. So same php version, Joomla upated to the same version (3.9.26), using same jQuery version (in jquery.min.js it says v1.12.4-joomla).

Anyone any idea what or which setting could cause this? I would really appreciate it, because I have no idea any more.

EDIT:

I inspected the $_POST and the $_GET variables: url parameters 'option' and 'task' are present (in $_GET) on both sites, but url parameter 'ajaxData' is only present (in $_POST) on one of the sites.

The .htaccess files are exactly the same on both sites.

Answer 1

in such cases I would inspect the $_POST variable to see if anything even gets into Joomla. This is to rule out something is happening within Joomla.

This can be as simple as this pirce of code into your index.php file. This will give a nice formatted output of everything that is posted.

?><pre><?php
echo __FILE__ . '::' . __LINE__ . ':: ';
echo 'POST: ';
echo '<div style="font-size: 1.5em;">';
print_r($_POST);
echo '</div>';
?></pre><?php
exit();

This way you will know if you need to look at the server or further at the code. In case you have XDebug that would be even better, you can put a breakpoint at where you want to stop in the code.

If you see the ajaxData in that output, you know that it reached the site. If you do not see the ajaxData there is most likely something on the server filtering it out. For example the .htaccess might be doing a redirect and thereby losing the payload.

Answer 2

I overlooked a rewrite rule in .htaccess that was actually different between both sites. This rewrite rule caused a 301 redirect. The GET parameters, which are in the url itself, were copied to the newly formed url by the rewrite rule, but the POST parameters got lost, because they are not passed on to the new url in a redirect.

Removing this (incorrect) rewrite rule from .htaccess solved the problem.