I am currently developing a Wordpress plugin handling very specific behaviours in our new Wordpress website. I started by reading the introduction articles in the Codex, and I also found the Wordpress plugin boilerplate. It is said that

to avoid function and variable collisions, we should enclose our functions inside a class, which should be named after our plugin.

The boilerplate already seems to handle that, fine!

However, I also expect to use third party libraries for my plugin (Swiftmailer, Mixpanel, etc.), which will be placed in '/wp-content/plugins/myplugin/includes'.

My question is, what if an other plugin also uses one of those libraries in its code? Swiftmailer is a pretty common library, so an other library could load it when initialized. There will be a collision (a class cannot be redefined in PHP). Are there mechanism in Wordpress to handle that ? Or does somebody already have a solution for this kind of issue ?

  • Can you check that the library (either the class or a function within the class) exists before including the library? Commented May 5, 2014 at 18:25

1 Answer 1


I have had to do this before, and what I find the easiest for me to do is something like this:

    function check_for_library() {
        return class_exists( 'Class_Of_Library_In_Question' );

Then you just fill in the right details and make a call to this function.

    if( ! check_for_library() ) {
        include_once( 'library_file.php' );

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