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Topic Tags: Compatibility

Overview of the issue

We have noticed that there are some customers reporting a fatal error on activating WPML

PHP Fatal error: Call to undefined method Composer\\Autoload\\ClassLoader::setPsr4() in .../wp-content/plugins/sitepress-multilingual-cms/embedded/composer/autoload_real.php on line 33

This issue happens from one of your other plugins using an outdated version of Composer, where the autoloader does not support setPsr4() method.

The problem happens when a plugin with such old version bundled is initialized before WPML plugin.

You can read more details here:


To fix the issue you must first find the offending plugin: you can do it by disabling all plugins, except WPML, and then re-activating them one by one.

Then it is advisable that you seek updated version of that plugin: if the issue does not get resolved, contact the author and let him know about the issue.

3 Responses to “Fatal error on activation - Call to undefined method Composer\\Autoload\\ClassLoader::setPsr4”

  1. Hi
    I have just made an order #105965983683 for your multilingual and pay it by credit card €33.97 vat incl. but for some reason I cannot access to the content and di not receive any email form your, Could you explain why ?
    looking forward to your prompt reply
    Luigi Orsi Carbone

      • I do not have an account . I went straight to order the Multilingual via the purchase bottom here I was requested to enter my email and other billing account but for some reason the order did not get completed and I still dont have access the the Multilingual despite my credit card was debied and I received a receipt for the payment
        As said order #105965983683 for your multilingual paid it by credit card €33.97
        Please let me know how could I get access to the product
        Also I would like to receive the billing receipt addressed to my company as I specified during the order or:
        Orsi & Partners Srl
        Via Passalacqua 15
        15057 Tortona (AL)
        VAT 13165760151
        Please let me know
        Luigi Orsi Carbone