MagicMethod in PHP

This article describes MagicMethod in PHP, including _ construct (), _ destruct (), and _ call (), _ callStatic (), _ get (), _ set (), _ toString (), etc. For more information, see 1. _ construct () and _ destruct ()

If an instance is called when it is created or destroyed, zero or multiple parameters can be passed.

class A {  function A()  {   echo "build A";  }   function __destruct()  {   echo "destroy A";  } }  $obj = new A(); //unset($obj);

Note: The destructor method will be called as soon as there are no other references to a participant object, or in any order during the shutdown sequence.

With regards to Constructor, a class defined in a particular namespace named after the class name will no longer be considered as a constructor at the beginning of PHP5.3.3. In a namespace-free class, it is still a constructor. For example:

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

If namespace Foo; is not available, Bar () is also 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 is, if _ construct () and a function with the same name as the class name are included, only _ construct () is called ().

2. _ call () and _ callStatic ()

This method is called when you try to call a method that does not exist. 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 $name is case sensitive.    echo "Calling object method '$name' "       . implode(' ', $arguments). "
";  }   public static function __callStatic($name, $arguments)  {    // Note: value of $name is case sensitive.    echo "Calling static method '$name' "       . implode(' ', $arguments). "
";  }} $obj = new MethodTest;$obj->runTest('in','object','context');MethodTest::runTest('in','static','context');

$ Arguments is passed as an array. Running result:

Calling object method 'runtest' in object context
Calling static method 'runtest' in static context

Also note the function scopes 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: * TestMagicCallMethod::__call * TestMagicCallMethod::baz */

3. _ get () and _ set ()

It is called when you try to read an attribute that does not exist in an object.

Note: We can use this function to perform operations similar to 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 exists
Name = abc

4. _ toString ()

This method is similar to the toString () method of java. when we print the object directly, we call this function back. The function must return a string.

class Test{  private $name = "abc";  private $age = 12;   public function __toString()  {    return "name : $this->name, age : $this->age";  }} $t = new Test();echo $t;

Output:

Name: abc, age: 12

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