A concise summary of magic methods in the PHP class (Magic Method)

1. __construct () and __destruct ()

Called when an instance is created/destroyed, it 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 will be called as soon there are no other references to a particular object, or in any order during the shutdown sequence.

With regard to constructors, starting with PHP 5.3. 3, a method named after the class name in class defined in a specific namespace will no longer be considered a constructor. In a class without namespace, it is still a constructor like the original 1. Such as:

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

function __construct()
  {
   echo "construct A";
  }

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

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

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

2. __call () and __callStatic ()

This method is called when an attempt is made to call a method that does not exist. Two parameters, one is the method name and one 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). "<br>";
  }

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

$obj = new MethodTest;
$obj->runTest('in','object','context');
MethodTest::runTest('in','static','context');

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

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."<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 trying to read a property of an object that does not exist.

Note: We can use this function to implement various operations 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."<br>";
$t->name = "abc";

Output:
name not exists
name = abc

4. __toString()

This method is similar to the toString () method of java. This function is called back when we print the object directly. The function must return 1 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