Why Do I Get the \"Declaration of Methods Should Be Compatible with Parent Methods\" Error in PHP?

Understanding "Declaration of Methods Should Be Compatible with Parent Methods" Error in PHP

When working with object-oriented programming in PHP, you may encounter the error "Strict Standards: Declaration of childClass::customMethod() should be compatible with that of parentClass::customMethod()." This error indicates that the declaration of a method in a child class must align with the declaration of the corresponding method in its parent class.

Possible Causes:

The error can occur due to two primary reasons:

• Argument Mismatch: The method in the child class has different input parameters (arguments) compared to the parent method. This includes differences in the number, type, or order of arguments.
• Access Level Discrepancy: The access level (public, private, or protected) of the method in the child class is not the same as that of the parent method. For example, a method declared as "public" in the parent class cannot be declared as "private" in the child class.

Compatible Method Declaration:

To ensure compatibility, the declaration of a method in the child class should match the declaration in the parent class in the following aspects:

• Input parameters (number, type, order)
• Return type
• Access level

Documentation and Resources:

• [Official PHP Manual: Method Overloading](https://www.php.net/manual/en/language.oop5.overloading.php)
• [PHPStan: Basic Level Method Compatibility](https://phpstan.org/user-guide/rules/methods/basic-method-compatibility)
• [Stack Overflow: What does the "Declaration of Method class::method should be compatible with that of parentClass::method" mean?](https://stackoverflow.com/questions/2194559/what-does-the-declaration-of-method-classmethod-should-be-compatible-with-that)

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