Solve PHP error: problems encountered when inheriting parent class

Solution to PHP error: Problems encountered when inheriting parent classes

In PHP, inheritance is an important feature of object-oriented programming. Through inheritance, we can reuse existing code and extend and improve it without modifying the original code. Although inheritance is widely used in development, sometimes you may encounter some error problems when inheriting from a parent class. This article will focus on solving common problems encountered when inheriting from a parent class and provide corresponding code examples.

Problem 1: Parent class not found

During the process of inheriting the parent class, if the system cannot find the file or class name that defines the parent class, the inheritance will fail and an error will be reported. This is usually caused by incorrect spelling of the file path or class name, or by namespace issues. The following is a sample code:

// 父类定义
class Father {
    // ...
}

// 子类定义
class Son extends Father {
    // ...
}

In the above code, if the definition of the parent class Father cannot be found, it may be because the file path is incorrect, or the parent is ignored when using the namespace. The namespace in which the class resides. The way to solve this problem is to confirm that the path of the parent class file is correct, and use the use statement to introduce the namespace of the parent class according to the actual situation.

Question 2: The parent class method does not exist

After inheriting the parent class, we can continue to extend and improve the parent class method, or we can override the parent class method. However, if a parent class method is called in a subclass and the parent class method does not exist or has been deleted, an error will be reported. The following is a sample code:

// 父类定义
class Father {
    public function getName() {
        return "father";
    }
}

// 子类定义
class Son extends Father {
    public function getName() {
        return "son";
    }
}

$son = new Son();
echo $son->getName();  // 输出：son
echo $son->showName();  // 报错：Call to undefined method Son::showName()

In the above code, the parent class Father has the method getName(), and the subclass Son has the method Son Rewritten and improved. When calling the getName() method, the correct output is "son". However, when calling the

method, an error "Call to undefined method Son::showName()" is reported. This is because the method is not defined in the parent class. The solution to this problem is to confirm that the parent class method being called exists and check that the method name is spelled correctly.

Question 3: Constructor calling error

When a subclass inherits a parent class, if the parent class has a constructor, the subclass should call the parent class's constructor when instantiated. If a constructor is not added to the subclass, or the parent class constructor is not called correctly, an error may result. The following is a sample code: <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class='brush:php;toolbar:false;'>// 父类定义 class Father { public function __construct() { // ... } } // 子类定义 class Son extends Father { // ... } $son = new Son(); // 报错：Fatal error: Uncaught Error: Call to undefined method Son::__construct()</pre><div class="contentsignin">Copy after login</div></div>In the above code, the parent class <code>Father has a constructor __construct(), and the subclass Son It does not define its own constructor, nor does it call the parent class constructor. Therefore, when instantiating the subclass Son, the error "Fatal error: Uncaught Error: Call to undefined method Son::__construct()" will be triggered. The way to solve this problem is to confirm that the constructor of the parent class is called, and add the constructor in the child class and call parent::__construct()

.

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