A concise summary of Magic Method in PHP classes
1. __construct() and __destruct()
are 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";
}
}
$obj = new A();
//unset($obj);
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.
Regarding constructors, starting from PHP 5.3.3, 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. 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 situation exists:
function __construct()
{
echo "construct A";
}
function A()
{
echo "build A";
}
function __destruct()
{
echo "destroy A";
}
}
contains both __construct() and a function with the same name as the class name, then only __construct( ).
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 $name is case sensitive.
echo "Calling object method '$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');
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
*/
$test->baz();
/**
* Outputs:
* TestMagicCallMethod::__call
* TestMagicCallMethod::baz
*/
3.__get() and __set()
are called when trying to read properties of an object that do not exist.
Note: We can use this function to implement various operations similar to reflection in java.
class Test
{
public function __get($key)
{
echo $key . " not exists";
}
public function __set($key,$value)
{
echo $key . " = ".$value;
}
}
$t = new Test();
echo $t->name."<br>";
$t->name = "abc";
Output:
name not exists
name = abc
4. __toString()
This method is similar to Java's toString() method. When we print the object directly, we call this function. 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
More magic methods in PHP classes (Magic Method) for a concise summary of related articles, please pay attention to the PHP Chinese website!
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