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WordPress: How to disable a plugin on all pages except for a specific one

A few days ago we were struggling to find a way to limit the amount of plugins that load at any point on a WordPress website. We noticed that several plugins enqueue their scripts and their styles in all requests to the website even if they are actually used on a single page only. This issue was important to address as it was making the whole server slower by giving it extra requests from the client that would never provide any actual benefit to the user.

Initially, we tried to selectively enable those plugins on their respective pages but we did not get it right and things would load out of order and break. Instead of following the ‘enable when needed‘ methodology we decided to follow the ‘disable unless needed‘ methodology which seemed simpler at the time.

Our changes involved in adding the following code in the functions.php file of our child theme.

//Register a filter at the correct event
add_filter( 'option_active_plugins', 'bf_plugin_control' );

function bf_plugin_control($plugins) {
  // If we are in the admin area do not touch anything
  if (is_admin()) {
    return $plugins;
  }
  
  // Check if we are at the expected page, if not remove the plugin from the active plugins list
  if(is_page("csv-to-kml-cell-site-map") === FALSE){ 
    // Finding the plugin in the active plugins list
    $key = array_search( 'csv-kml/index.php' , $plugins );
    if ( false !== $key ) {
      // Removing the plugin and dequeuing its scripts
      unset( $plugins[$key] );
      wp_dequeue_script( 'bf_csv_kml_script' );
    }
  }

  if(is_page("random-password-generator") === FALSE){ 
    $key = array_search( 'bytefreaks-password-generator/passwordGenerator.php' , $plugins );
    if ( false !== $key ) {
      unset( $plugins[$key] );
    }
  }
  
  if(is_page("xml-tree-visualizer") === FALSE){ 
    $key = array_search( 'xmltree/xml-tree.php' , $plugins );
    if ( false !== $key ) {
      unset( $plugins[$key] );
      wp_dequeue_script( 'bf_xml_namespace' );
      wp_dequeue_style( 'bf_xml_namespace' );
    }
  }

  return $plugins;
}

One day, we will clean the above code to make it tidy and reusable.. one day, that day is not today.

What the code above does is the following:

  • Using is_admin it checks if the Dashboard or the administration panel is attempting to be displayed, in that case it does not do any changes.
  • With is_page, it will additionally check if the parameter is for one of the pages specified and thus disable the plugin if the check fails.
  • PHP command array_search, will see if our plugin file is expected to be executed (all files in $plugins are the plugin files that are expected to be executed) .
  • wp_dequeue_script and wp_dequeue_style remove the previously enqueued scripts and styles of the plugin as long as you know the handles (or namespaces of the enqueued items).
    To get the handles (namespaces) we went through the plugin codes and found all instances of wp_enqueue_script and wp_enqueue_style.
    Please note that several small plugins do not have additional items in queue so no further action is needed.


Starting XAMPP with port 80 on Windows 10 Professional

Recently we were asked to have a look at a XAMPP installation on a Windows 10 Professional machine which would not start while giving the following error:

Problem detected!
Port 80 in use by "Unable to open process" with PID 4!
Apache WILL NOT start without the configured ports free!
You need to uninstall/disable/reconfigure the blocking application
or reconfigure Apache and the Control Panel to listen on a different port

The culprit of this problem was a module of the IIS (Internet Information Services for Windows Server) that is named World Wide Web Publishing Service (WWW service or W3SVC service). Apparently, the W3SVC was hoarding port 80 even though IIS was not executing. To provide a quick solution, we decided to stop the W3SVC and get over this difficulty in a jiffy.

As you can see in the following video, to stop the World Wide Web Publishing Service (WWW service or W3SVC service) we performed the next steps:

  1. Clicked on the Start button
  2. Typed in the word services, which showed the Services link which we clicked to start the windows services  manager
  3. Then, we scrolled down in the Services window until we found the World Wide Web Publishing Service
  4. Finally, we right clicked on it and selected Stop.

After that, XAMPP was able to start Apache on port 80 with no issues.

 


How to create a video from thousands of images using ffmpeg

We have this simulation that creates several frames demonstrating the life-cycle of an ant colony.
Having thousands of pictures is not very useful most of the times so we decided to create a video out of those frames.
To do so, we decided to use ffmpeg. The names of the files that we generate are 5 digit zero-leading auto increment numbers (e.g 00001.png and 00002.png) so we ended up with the following command:

ffmpeg -framerate 60 -i %05d.png video.mp4;


How to create a video from an audio file and an image using ffmpeg

Recently, we had this audio file ( mp3) that we wanted to upload to youtube.com. As it is known, youtube does not allow uploading audio files. Taking that into consideration we had to create a video with a static image just to upload the audio file to youtube. To do that, we used ffmpeg and the following command:

ffmpeg -loop 1 -i Saturday.png -i 20181020.mp3 -shortest -acodec copy 20181020.mp4;