The Magic Method in PHP

1. __construct () and __destruct ()

It is called when the instance is created/destroyed, and can pass 0 or more parameters.

  Class A  {    function A ()    {      echo "build a";    }    function __destruct ()    {      echo "destroy A";    }  }  $obj = new A ();  

Note:the destructor method would be called as soon as there is no other references to a particular object, or in any order During the shutdown sequence.

With regard to constructors, PHP5.3.3, a method defined in a class named in a particular namespace is no longer considered a constructor. The constructor is still the same as the original in the namespace-free class. Such as:

Namespace Foo;class Bar {public    function bar () {        //treated as constructor in PHP 5.3.0-5.3.2        //treated a s regular method as of PHP 5.3.3    }}

If there is no namespace Foo; Bar () will also be used as a constructor. In addition, if the following conditions exist:

  function __construct ()    {      echo "construct A";    }    function A ()    {      echo "build A";    }    function __destruct ()    {      echo "destroy A";    }  }

That is, contains both __construct () and a function with the same name as the class name, then only __construct () is called.

2. __call () and __callstatic ()

This method is called when an attempt is to invoke a nonexistent method. Two parameters, one is the method name, and the other is the parameter array of the called method.

Class methodtest{public    function __call ($name, $arguments)    {        //Note:value of $name are case sensitive.        echo "Calling object method ' $name '"             . Implode (", $arguments). "
";    }    public static function __callstatic ($name, $arguments)    {        //Note:value of $name are case sensitive.        echo "Calling static method ' $name '"             . Implode (", $arguments). "
";    

Where $arguments is passed in as an array. Operation Result:

Calling object method ' Runtest ' in Object contextcalling static method ' Runtest ' in static context

Also note the scope of the function protected and private:

Class Testmagiccallmethod {public    function foo ()    {        echo __method__. Php_eol. "
";    }    Public Function __call ($method, $args)    {        echo __method__. Php_eol. "
";        if (Method_exists ($this, $method))        {            $this-$method ();        }    }       protected function Bar ()    {        echo __method__. Php_eol. "
";    }    Private function Baz ()    {        echo __method__. Php_eol. "
";    }} $test    =    new Testmagiccallmethod (); $test->foo ();/** * Outputs: * Testmagiccallmethod::foo */$test Bar ();/** * Outputs: * Testmagiccallmethod::__call * testmagiccallmethod::bar * * $test->baz ();/** * Outputs: * Testmagi Ccallmethod::__call * Testmagiccallmethod::baz * *

3.__get () and __set ()

Called when attempting to read a property that does not exist for an object.

Note: We can use this function to implement various actions like reflection in Java.

Class test{public   function __get ($key)   {      echo $key. "Not exists";   }   Public Function __set ($key, $value)   {      echo $key. "=". $value;   }} $t = new Test (); Echo $t->name. "
"; $t->name =" abc "; output: Name not existsname = ABC

4. __tostring ()

This method is similar to the ToString () method of Java, and when we print the object directly, the callback uses this function, and the function must return a string.

Class test{    Private $name = "abc";    Private $age = n;    Public Function __tostring ()    {        return ' name: $this->name, Age: $this->age ";    }} $t = new Test (); Echo $t; output: Name:abc, Age:12

There are also __isset (), __unset (), __sleep (), __wakeup (), __tostring (), __invoke (), __set_state () and __clone () without repeating them.

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