Detailed explanation of magic method examples in OOP
本篇文章主要介绍了浅谈PHP中的面向对象OOP中的魔术方法 ,具有一定的参考价值,感兴趣的小伙伴们可以参考一下
一、什么是魔术方法:
PHP为我们提供了一系列用__开头的函数,这些函数无需自己手动调用,会在合适的时机自动调用,这类函数称为魔术函数。
例如:
function __construct(){}
在new一个新对象时自动调用此函数
二、PHP中都有那些魔术方法,以及它们的作用:
1.__construct():构造函数,new对象时自动调用
eg:
class Person{ public $name; public $age; function __construct($name,$age){ $this->name=$name; $this->age=$age; } }
在new新的Person对象时会自动调用__construct()函数,将传入的参数分别赋给$name,$age。
2.__destruct():析构函数,当一个对象被销毁前自动调用
class Person{ public $name; public $age; function __destruct(){ echo "这个对象被销毁了"; } }
同上所述,对象被销毁时执行此魔术方法
3.__get():访问类中私有属性时自动调用,传递读取属性名,返回$this->属性名
class Person{ private $name; public $age; function __get($name){ return $this->$name; } }
如上代码,$name被设为私有属性后不能直接通过$this->name;的方式读取,因此需要设置__get()魔术方法来读取。
4.__set():给类的私有属性赋值时自动调用,传递需设置的属性名,属性值
class Person{ private $name; public $age; function __set($key,$value){ $this->$key=$value; } }
同__get()方法,私有属性不能通过$this->name="aaa";的方式直接设置,需要设置__set()方法,传入的参数分别是属性名和属性值。
5.__isset():使用isset检测对象私有属性时调用,传递检测的属性名,返回isset($this->属性名)
class Person{ private $name; public $age; function __isset($name){ return isset($this->$name); } }
使用isset检测对象私有属性时调用,其他同上。
6.__unset():使用unset()函数删除对象私有属性时调用,传递删除的属性名,方法中执行unset($this->属性名)
class Person{ private $name; public $age; function __unset($name){ unset($this->$name); } }
同上,在用unset()函数删除私有属性时调用。
7.__toString():使用echo打印对象时调用,返回打印对象时想要显示的内容,返回必须是字符串
class Person{ public $name; public $age; function __toString(){ $str = <<<str 您要打印的内容是:<br> \$name=>{$this->name};<br> \$age=>{$this->age};<br> str; return $str; } }
使用echo打印对象时调用,返回打印对象时想要显示的内容。
8.__call():调用一个类中未定义的或未公开的方法时自动调用,传递被调用的函数名及参数列表
class Person{ public $name; public $age; function __call($funcName,$funcParams){ echo "您调用的函数{$funcName},参数列表"; print_r($funcParams); echo "不存在/未公开"; } } $zhangsan=new Person(); $zhangsan->say(1,2,3);
如代码所示,调用不存在的say(1,2,3);时,会打印
您调用的函数way,参数列表Array ( [0] => 123 ) 不存在
9.__clone():当使用clone关键字,克隆一个对象时自动调用,作用是为新克隆的对象初始化赋值
class Person{ public $name; public $age; function __clone(){ $this->name="lisi"; } } $zhangsan=new Person("zhangsan",24); $lisi=clone $zhangsan; echo $lisi->name;
打印出的结果是"lisi",而不是"zhangsan"。
10.__sleep():对象序列化时自动调用,返回一个数组,数组中的值就是可以序列化的属性
class Person{ public $name; public $age; function __sleep(){ return array("name","age"); } }
如上述代码,在用serialize()序列化对象时只有"name","age"属性会被序列化。
11.__wakeup():对象反序列化时自动调用,为反序列化新产生的对象进行初始化赋值
class Person{ public $name; public $age; function __wakeup(){ $this -> name = "lisi"; } }
将对象序列化后再反序列化,同时给对象的name属性赋初值为"lisi"。
12.__autolode():需要在类外部声明函数,当实例化一个未声明的类时自动调用,传递实例化的类名,可以使用类名自动加载对应的类文件。
function __autoload($className){ include "class/".strtolower($className).".class.php"; } $zhangsan=new Person(); $zhangsan->say();
如上述代码,Person类不存在时调用__autolode()方法,载入写在文件外的类,"class/".strtolower($className).".class.php";就是类文件的相对路径,$className就是
不在本文件中的类的类名,因此在创建外部类文件时命名方式必须是小写的类名.class.php。__autolode()方法也是惟一一个不用写在类中的魔术方法。
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