Detailed explanation of php object-oriented __toString() usage_PHP tutorial

This article will introduce to you the detailed usage of PHP object-oriented __toString(). The __toString() method is automatically called when directly outputting an object reference

As we said before, the method of declaring the method name starting with "--" in the class (provided to us by PHP) is a method that is automatically called and executed under different circumstances at a certain time. The "__toString()" method is also automatically The one that is called is automatically called when the object reference is output directly. We mentioned earlier that the object reference is a pointer. For example, in "$p=new Person()", $p is a reference. We cannot use echo directly. Output $p, which will output an error like "Catchable fatal error: Object of class Person could not be converted to string". If you define the "__toString()" method in the class, when you directly output the object reference, No error will be generated, but the "__toString()" method is automatically called to output the characters returned in the "__toString()" method, so the "__toString()" method must have a return value (return statement).

Code

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代码如下	复制代码
// Declare a simple class     class TestClass     {         public $foo;         public function __construct($foo) {         $this->foo = $foo;         }        //定义一个__toString方法，返加一个成员属性$foo         public function __toString() {         return $this->foo;         }     }     $class = new TestClass('Hello');     //直接输出对象     echo $class; ?>

// Declare a simple class class TestClass {         public $foo; public function __construct($foo) { $this->foo = $foo; } //Define a __toString method and return a member attribute $foo           public function __toString() {           return $this->foo; } } $class = new TestClass('Hello'); //Directly output the object echo $class; ?>

It seems familiar. In the magic method __set of PHP object-oriented programming, I once introduced what a magic method is. This chapter also introduces a magic method __tostring().

__toString() is a convenient way to quickly obtain the string information of an object. It seems that magic methods have an "automatic" feature, such as automatic acquisition, automatic printing, etc. __toString() is no exception. It directly outputs the object reference. Automatically called method.

The function of __toString()

When we debug a program, we need to know whether we are getting the correct data. For example, when printing an object, see what attributes the object has and what their values ​​are. If the class defines the toString method, you can echo print the object body during testing, and the object will automatically call the toString method defined by the class it belongs to. , format and output the data contained in this object.

Let’s look at an example of __toString()

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代码如下

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02 class Person{  03     private $name = "";  04     function __construct($name = ""){  05                     06         $this->name = $name;  07     }  08     function say(){  09                     10         echo "Hello,".$this->name."! ";    11     }  12     function __tostring(){//在类中定义一个__toString方法  13         return  "Hello,".$this->name."! ";      14     }  15 }  16 $WBlog = new Person('WBlog');  17 echo $WBlog;//直接输出对象引用则自动调用了对象中的__toString()方法  18 $WBlog->say();//试比较一下和上面的自动调用有什么不同  19 ?> 程序输出： Hello,WBlog! Hello,WBlog!

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02 class Person{

03 private $name = "";

04 function __construct($name = ""){

06 $this->name = $name;

07 }

08 function say(){ 09                                                                         10 echo "Hello,".$this->name."!
"; 11 } 12 function __tostring(){//Define a __toString method in the class 13 return "Hello,".$this->name."!
"; 14 }

15 }

16 $WBlog = new Person('WBlog');

17 echo $WBlog;//Directly outputting the object reference automatically calls the __toString() method in the object 18 $WBlog->say(); // Try to compare the difference with the automatic call above 19 ?> Program output: Hello,WBlog! Hello,WBlog! What happens if the "__tostring()" method is not defined? For example, based on the above code, block the "__tostring()" method, and then look at the program output: Catchable fatal error: Object of class Person could not be converted to string It can be seen that if the "__tostring()" method is not defined in the class, a syntax error will occur when directly outputting an object reference. In addition, there needs to be a return value in the __tostring() method body. http://www.bkjia.com/PHPjc/632687.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/632687.htmlTechArticleThis article will introduce to you students about the detailed usage of php object-oriented __toString(), __toString() method It is automatically called when directly outputting an object reference...