PHP 魔术方法

• __sleep，__wakeup
__sleep 在使用 serialize 方法进行序列化之前调用，返回需要进行序列化保存的属性数组，如果属性不在该数组里，存储的是属性的默认值，一般执行一些释放清理比较大变量的工作。
  __wakeup 在使用 unserialize 方法进行反序列化后调用，一般是生成对象后执行初始化工作。
  Test.php

<?php

class Test
{
    public $a = 'A';
    protected $b = 'I am B';
    private $c = 'B';

    public function __construct()
    {
        $this->a='I am A';
        $this->b=520;
        $this->c="I am C";
    }

    public function test()
    {
        echo "\ntest method\n";
        echo $this->a;
        echo $this->b;
        echo $this->c;
    }

    public function __sleep()
    {
        return ['a','c'];
    }

    public function __wakeup()
    {
        $this->test();
    }
}


$test = new Test();
echo "\nserialize\n";
$s = serialize($test);
var_export($s);
echo "\nunserialze\n";
$o = unserialize($s);
var_export($o);

执行结果

serialize
'O:4:"Test":2:{s:1:"a";s:6:"I am A";s:7:"' . "\0" . 'Test' . "\0" . 'c";s:6:"I am C";}'
unserialze

test method
I am AI am BI am CTest::__set_state(array(
   'a' => 'I am A',
   'b' => 'I am B',
   'c' => 'I am C',
))

• __serialize，__unserialize
  这两个魔术方法 php7.4才支持，功能类似 __sleep 和 __wakeup，不过 __serialize 返回的是属性的 key => value 数组，__unserialize 需要手动解析数据
• __toString
  把对象当字符串打印时会执行该方法，并且需要返回一个字符串

 <?php

class Test
{
    public $a = 'I am a string';

    public function __toString()
    {
        return $this->a;
    }
}
$o = new Test();
echo $o;

输出结果：I am a string

• __invoke
  当将对象当方法来调用时会触发该方法

<?php

class Test
{
    public function __invoke($a, $b)
    {
        echo "Hello, I am from invoke\n";
        echo "\n{$a}\n";
        var_export(func_get_args());
    }
}

$o = new Test();
$o("A","B", "C");

结果

Hello, I am from invoke

A
array (
  0 => 'A',
  1 => 'B',
  2 => 'C',
)

• __set_state
  var_export 打印对象时会调用

<?php

class Test
{
    public $a;
    protected $b;
    private $c;

    public function __construct()
    {
        $this->a = 'AAA';
        $this->b = 'BBB';
        $this->c = 'CCC';
    }

    public function __set_state($data)
    {
        $o = new stdClass();
        $o->d = $data['a'];
        $o->e = $data['b'];
        $o->c = $data['c'];
        return $o;
    }
}
$o = new Test();
$result = var_export($o, true);
eval('$tmp = ' . $result . ";");
var_export($tmp);

结果

stdClass::__set_state(array(
   'd' => 'AAA',
   'e' => 'BBB',
   'c' => 'CCC',
))

• __construct
  实例化对象时执行构建函数
• __destruct
  当对象引用被删除时，执行析构函数
• __set ，__get ，__isset，__unset
__set 当对象设置一个不可访问属性或者不存在的属性名时，会触发该函数
  __get 当对象获取一个不可访问属性或不存在属性值时，会触发该函数
  __isset 判断对象属性是否存在，当属性是不可访问或不存在时会触发
  __unset 释放对象属性，当属性不可访问或不存在时会触发

<?php

class Test
{
    public $a = 'AAA';
    private $b = 'BBBB';

    public function __set($key, $value)
    {
        echo "set {$key}={$value}\n";
        $this->$key = $value;
    }

    public function __get($key)
    {
        echo "get {$key}=" . $this->$key;
    }

    public function __isset($name)
    {
        echo "trigger isset {$name}\n";
    }


    public function __unset($name)
    {
        echo "trigger unset {$name}\n";
    }
}

$o = new Test();
$o->a="I am A\n";
$o->b="I am B\n";
$o->c="I am C\n";
echo $o->a . "\n";
echo $o->b . "\n";
echo $o->c . "\n";
echo $o->d . "\n";

var_export(isset($o->a));
echo "\n";
var_export(isset($o->b));
echo "\n";
var_export(isset($o->c));
echo "\n";
var_export(isset($a->d));
echo "\n";

unset($o->a);
unset($o->b);
unset($o->c);
unset($o->d);

结果

set b=I am B

set c=I am C

I am A

get b=I am B

I am C

PHP Notice:  Undefined property: Test::$d in /Users/songzw/Downloads/require-include/call-static/set-get-test.php on line 16
get d=
true
trigger isset b
false
true
false
trigger unset b
trigger unset d

• __call，__callStatic
__call 当对象调用一个不存在的方法时会触发该函数
  __callStatic 当类调用一个不存在的类方法时会触发该函数

<?php

class Test
{
    public function __call($method, $args)
    {
        echo "call method={$method},args=" . implode(',',$args) . "\n";
    }

    public static function __callStatic($method, $args)
    {
        echo "callStatic method={$method},args=" . implode(',',$args) . "\n";
    }

}

$o = new Test();
$o->test1('aaa','bbb');
Test::testStatic1('ccccc','dddddd');

结果

call method=test1,args=aaa,bbb
callStatic method=testStatic1,args=ccccc,dddddd

• __clone
  当使用 clone 来复制对象时，会触发该函数，可用于禁止拷贝对象或拷贝时修改属性

本作品采用《CC 协议》，转载必须注明作者和本文链接