The Magic method in PHP Class (Magic methods) Concise summary _php instance

1. __construct () and __destruct ()

Invoked when an instance is created/destroyed, you can pass 0 or more parameters.

Class A
 {
  function A ()
  {
   echo "build A";
  }

  function __destruct ()
  {
   echo "destroy A";
  }
 }

 $obj = new A ();
 Unset ($obj);

Note:the destructor method would be called as soon as there are no other references to a particular object During the shutdown sequence.

With respect to constructors, PHP5.3.3 begins, a method that is defined as a class name in a particular namespace is no longer considered a constructor. In a class that is not namespace, it is still a constructor. Such as:

namespace Foo;
Class Bar {public
  function bar () {
    //treated as constructor in PHP 5.3.0-5.3.2
    //treated as regular meth Od as of PHP 5.3.3
  }
}

If there is no namespace Foo; Then bar () will also be treated 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 contains both __construct () and a function with the same name as the class name, only the __construct () is invoked.

2. __call () and __callstatic ()

This method is called when an attempt is to invoke a method that does not exist. Two parameters, one is the method name, and one is the parameter array of the invoked method.

Class Methodtest
{public
  function __call ($name, $arguments)
  {
    //Note:value of $name was case sensit Ive.
    echo "Calling object method ' $name '"
       . Implode (", $arguments). "<br>";
  }

  public static function __callstatic ($name, $arguments)
  {
    //Note:value of $name was case sensitive.
    echo "Calling static method ' $name '"
       . Implode (", $arguments). "<br>";
  }

$obj = new Methodtest;
$obj->runtest (' in ', ' object ', ' context ');
Methodtest::runtest (' In ', ' static ', ' context ');

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

Calling object method ' Runtest ' in the object context
Calling static method ' Runtest ' in the static context

Also note the scope of the function protected and private:

Class Testmagiccallmethod {public
  function foo ()
  {
    echo __method__. Php_eol. " <br> ";
  }

  Public Function __call ($method, $args)
  {
    echo __method__. Php_eol. " <br> ";
    if (Method_exists ($this, $method))
    {
      $this-> $method ();
    }
  }
  
  protected function Bar ()
  {
    echo __method__. Php_eol. " <br> ";
  }

  Private function Baz ()
  {
    echo __method__. Php_eol. " <br> ";
  }
}

$test  =  new Testmagiccallmethod ();
$test->foo ();
/**
 * Outputs:
 * testmagiccallmethod::foo

/$test->bar ();
/**
 * Outputs:
 * testmagiccallmethod::__call
 * Testmagiccallmethod::bar
 /

$test->baz ();
/**
 * Outputs:
 * testmagiccallmethod::__call
 * Testmagiccallmethod::baz
 *

3.__get () and __set ()

Called when an attempt is made to read a property that does not exist for an object.

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

Class Test
{public
  function __get ($key)
  {
   echo $key. "Not exists";
  }
  The Public Function __set ($key, $value)
  {
   echo $key. "=". $value;
  }
}

$t = new Test ();
echo $t->name. " <br> ";
$t->name = "abc";

Output:
Name NOT EXISTS
name = ABC

4. __tostring ()

This method is similar to the Java ToString () method, 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 =;

  Public Function __tostring ()
  {return
    ' name: $this->name, Age: $this->age ';
  }
}

$t = new Test ();
Echo $t;

Output:

NAME:ABC, Age:12