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

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2024-11-02 07:00:30366browse

Why Do I Get the

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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