PHP Object-oriented __tostring () usage detailed _php tutorial

This article to introduce to you about PHP object-oriented __tostring () usage, the __tostring () method is automatically called, is the direct output object reference when automatically called

As we said earlier in the class, the method of declaring "--" The Starting method name (provided by PHP to us) is automatically invoked at some point in different situations, and the "__tostring ()" method is also automatically called, which is called automatically when the object reference is directly exported. We said before that the object reference is a pointer, for example: "$p =new person ()", $p is a reference, we can not use the Echo Direct output $p, this will output "catchable fatal error:object of class person Could not being converted to string "error, if you define" __tostring () "method in the class, when the direct output object reference, will not produce an error, but automatically called the" __tostring () "Method, Output" _ The character returned in the _tostring () "method, so the" __tostring () "method must have a return value (return statement).

Code

The code is as follows	Copy Code
Declare a simple class Class TestClass { Public $foo; Public function __construct ($foo) { $this->foo = $foo; } Define a __tostring method and return a member property $foo Public Function __tostring () { return $this->foo; } } $class = new TestClass (' Hello '); Direct Output Object Echo $class; ?>

Déjà vu, in the PHP object-oriented Programming Magic method __set, once introduced what is the Magic method, this chapter introduces a magic Method __tostring ().

__tostring () is a quick way to get the string information of an object quickly, and it seems that the magic method has an "automatic" feature, such as automatic acquisition, automatic printing, and so on, __tostring () is no exception, it is the method that is called automatically when the object reference is directly exported.

The role of __tostring ()

When we debug the program, we need to know if we can get the correct data. For example, when printing an object, look at the properties of this object, what the value is, if the class defines the ToString method, in the test, echo prints the object body, the object will automatically call its own class definition of the ToString method, formatted output this object contains data.

Let's look at an example of a __tostring ()

code as follows

copy code

"!--? php Class person{ Private $name = ""; Function __construct ($name = "") { $this->name = $name; " " function say () { " " echo "Hello". $this->name. " "; One} Function __tostring () {//define a __tostring method in a class Return "Hello,". $this->name. "! "; + $WBlog = new Person (' wblog '); Echo $WBlog;//The Direct Output object reference automatically calls the __tostring () method in the object $WBlog->say ();//Compare what is different from the automatic call above . Program output: hello,wblog! hello,wblog!

What happens if you don't define the "__tostring ()" Method? For example, on the basis of the above code, the "__tostring ()" method to screen off, and then look at the program output results:

Catchable fatal error:object of class person could not being converted to string

It can be concluded that if the "__tostring ()" method is not defined in the class, the error is generated by the direct output of a reference to the image, and a return value is required in the __tostring () method body.

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