Pretty simple PHP conditional statement - I think [duplicate]

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• In PHP, how do I check if a function exists? 5 answers

This question is probably far too simple for a forum like this but I'm pretty much a novice. I'm learning a lot about running a website but haven't quite caught on to PHP yet. So...

I'm using a plugin and a bit of PHP code in the theme of my WP blog to put ads where I want them. This is an example of the code:

<?php echo adrotate_ad(4); ?>

Not too complicated but...

When the plugin is deactivated, this of course, returns a warning when trying to load the page.

I'm guessing I need a conditional statement that says if adrotate_ad(4) is not there then ignore the command? You can tell just how much I do not know.

Any help is appreciated. If I haven't given enough information, let me know. Please help a noob. Thanks.