PHP magic method application example code summary-PHP Tutorial-php.cn

PHP magic method application example code summary

伊谢尔伦

Release： 2023-03-12 06:16:01

Original

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This article mainly introduces a concise summary of Magic Method (Magic Method) in PHP classes. These methods include construct(), destruct(), call(), callStatic(), get() , set(), toString(), etc. Friends who need it can refer to

1. construct() and destruct()

when the instance is created/destroyed When called, zero or more parameters can be passed.

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

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

 $obj = new A();
 //unset($obj);

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

　AboutConstructor, starting from PHP5.3.3, a method named with the class name in a class defined in a specific namespace will no longer be considered a constructor. In a class without a namespace, it is still a constructor as before. 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
  }
}

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

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

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

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

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

2. call() and callStatic()

Called when trying 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 $name is case sensitive.
    echo "Calling object method &#39;$name&#39; "
       . implode(&#39; &#39;, $arguments). "<br>";
  }

  public static function callStatic($name, $arguments)
  {
    // Note: value of $name is case sensitive.
    echo "Calling static method &#39;$name&#39; "
       . implode(&#39; &#39;, $arguments). "<br>";
  }
}

$obj = new MethodTest;
$obj->runTest(&#39;in&#39;,&#39;object&#39;,&#39;context&#39;);
MethodTest::runTest(&#39;in&#39;,&#39;static&#39;,&#39;context&#39;);

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Among them, $arguments is passed in as an array. Running results:

Calling object method 'runTest' in object context
Calling static method 'runTest' in static context

Also pay attention to the scope protected and private of the function:

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
 */

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3.get() and set()

are called when trying to read properties of an object that do not exist.

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

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Output:
name not exists
name = abc

4. toString()

This method is similar to java toString() method, this function is called when we print the object directly. 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;

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Output:

name : abc, age : 12

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