How to Fix Call To Undefined Function Fatal Error

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Either a blank website page or a fatal error as shown in the example below:

Call to undefined function is_shop()


The only cause for this fatal error is that requested function does not exist in the scope of the executable code. In other words – your website simply does not know about the requested function. It is one of the most common errors when a website has multiple plugins installed that depend on each other.


In order to fix this fatal error, you should have good knowledge in PHP to debug the source code.

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This error can be automatically fixed with CodePinch. Download CodePinch on your website and within hours we will be able to provide you with solution.


The ideal way to resolve this error is to find out in what file or plugin the missing function is declared and make sure that it is included before the first call. With PHP 5.3.0 or higher, developers have a power to organized code with namespaces, that is why it is also important to be aware that the missing function is called within correct namespace.

The example below shows how to fix “call to undefined function” fatal error. This solution ensures that your website get executed even when a called function does not exist anymore in the website’s codebase.

@@ -11,9 +11,9 @@
- if (is_shop())) :
+ if ( function_exists('is_shop')  && is_shop())) :

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