Why Does My PHP Child Class Method Throw a 'Declaration of childClass::customMethod() should be compatible with that of parentClass::customMethod()' Error?

Understanding the Compatibility Requirement for Method Declarations in PHP

In PHP, when extending a class and defining a method with the same name as a parent method, it's crucial to ensure method compatibility. The error message "Declaration of childClass::customMethod() should be compatible with that of parentClass::customMethod()" indicates a conflict in the method's signature or accessibility level between the parent and child classes.

Possible Causes of the Error

There are two main reasons why this error may occur:

• Differing Method Arguments: The child method must have the same number and type of arguments as the parent method. Even minor differences can trigger this error.
• Access Level Mismatch: The access level of the child method must match or be less restrictive than that of the parent method. For example, if the parent method is public, the child method cannot be private.

Finding Information on Compatibility

The PHP documentation provides detailed information on the compatibility requirements for method declarations. Specifically, the following sections are valuable resources:

• [Method Declarations](https://www.php.net/manual/en/language.oop5.methods.php#language.oop5.methods.definition)
• [Visibility and Inheritance](https://www.php.net/manual/en/language.oop5.visibility.php)

By understanding the compatibility criteria and referring to the official documentation, you can effectively resolve this error and ensure that your code adheres to PHP's inheritance principles.

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