masyarakat Belajar Perpustakaan Alatan Masa lapang
cari
Melayu
Rumah > php教程 > php手册 > teks badan

PHP面向对象中的重要知识点(一)

WBOY
Lepaskan： 2016-06-06 19:36:10
asal
998 orang telah melayarinya

1. __construct: 内置构造函数，在 对象 被创建时自动调用。见如下代码： ? php class ConstructTest { private $arg1 ; private $arg2 ; public function __construct( $arg1 , $arg2 ) { $this -arg1 = $arg1 ; $this -arg2 = $arg2 ; print "__construct

1. __construct: 

     内置构造函数，在对象被创建时自动调用。见如下代码：

<span>php
</span><span>class</span><span> ConstructTest {
    </span><span>private</span> <span>$arg1</span><span>;
    </span><span>private</span> <span>$arg2</span><span>;

    </span><span>public</span> <span>function</span> __construct(<span>$arg1</span>, <span>$arg2</span><span>) {
        </span><span>$this</span>->arg1 = <span>$arg1</span><span>;
        </span><span>$this</span>->arg2 = <span>$arg2</span><span>;
        </span><span>print</span> "__construct is called...\n"<span>;
    }
    </span><span>public</span> <span>function</span><span> printAttributes() {
        </span><span>print</span> '$arg1 = '.<span>$this</span>->arg1.' $arg2 = '.<span>$this</span>->arg2."\n"<span>;
    }
}
</span><span>$testObject</span> = <span>new</span> ConstructTest("arg1","arg2"<span>); 
</span><span>$testObject</span>->printAttributes();
Salin selepas log masuk

     运行结果如下：

Stephens-<span>Air:Desktop$ php Test.php 
__construct is called...
$arg1 </span>= arg1 $arg2 = arg2
Salin selepas log masuk

2. parent: 

     用于在子类中直接调用父类中的方法，功能等同于Java中的super。 

<span>php
</span><span>class</span><span> BaseClass {
    </span><span>protected</span> <span>$arg1</span><span>;
    </span><span>protected</span> <span>$arg2</span><span>;

    </span><span>function</span> __construct(<span>$arg1</span>, <span>$arg2</span><span>) {
        </span><span>$this</span>->arg1 = <span>$arg1</span><span>;
        </span><span>$this</span>->arg2 = <span>$arg2</span><span>;
        </span><span>print</span> "__construct is called...\n"<span>;
    }
    </span><span>function</span><span> getAttributes() {
        </span><span>return</span> '$arg1 = '.<span>$this</span>->arg1.' $arg2 = '.<span>$this</span>-><span>arg2;
    }
}

</span><span>class</span> SubClass <span>extends</span><span> BaseClass {
    </span><span>protected</span> <span>$arg3</span><span>;

    </span><span>function</span> __construct(<span>$baseArg1</span>, <span>$baseArg2</span>, <span>$subArg3</span><span>) {
        parent</span>::__construct(<span>$baseArg1</span>, <span>$baseArg2</span><span>);
        </span><span>$this</span>->arg3 = <span>$subArg3</span><span>;
    }
    </span><span>function</span><span> getAttributes() {
        </span><span>return</span> parent::getAttributes().' $arg3 = '.<span>$this</span>-><span>arg3;
    }
}
</span><span>$testObject</span> = <span>new</span> SubClass("arg1","arg2","arg3"<span>); 
</span><span>print</span> <span>$testObject</span>->getAttributes()."\n";
Salin selepas log masuk

     运行结果如下：

Stephens-<span>Air:Desktop$ php Test.php 
__construct is called...
$arg1 </span>= arg1 $arg2 = arg2 $arg3 = arg3
Salin selepas log masuk

3. self:

     在类内调用该类静态成员和静态方法的前缀修饰，对于非静态成员变量和函数则使用this。 

<span>php
</span><span>class</span><span> StaticExample {
    </span><span>static</span> <span>public</span> <span>$arg1</span> = "Hello, This is static field.\n"<span>;
    </span><span>static</span> <span>public</span> <span>function</span><span> sayHello() {
        </span><span>print</span> self::<span>$arg1</span><span>;
    }
}

</span><span>print</span> StaticExample::<span>$arg1</span><span>;
StaticExample</span>::sayHello();
Salin selepas log masuk

     运行结果如下：

Stephens-<span>Air:Desktop$ php Test.php 
Hello, This is static field.
Hello, This is static field.</span>
Salin selepas log masuk

4. static:

     这里介绍的static关键字主要用于PHP 5.3以上版本新增的延迟静态绑定功能。请看一下代码和关键性注释。

<span>php
</span><span>abstract</span> <span>class</span><span> Base {
    </span><span>public</span> <span>static</span> <span>function</span><span> getInstance() {
        </span><span>//</span><span>这里的new static()实例化的是调用该静态方法的当前类。</span>
        <span>return</span> <span>new</span> <span>static</span><span>();
    }
    </span><span>abstract</span> <span>public</span> <span>function</span><span> printSelf(); 
}

</span><span>class</span> SubA <span>extends</span><span> Base {
    </span><span>public</span> <span>function</span><span> printSelf() {
        </span><span>print</span> "This is SubA::printSelf.\n"<span>;
    }
}

</span><span>class</span> SubB <span>extends</span><span> Base {
    </span><span>public</span> <span>function</span><span> printSelf() {
        </span><span>print</span> "This is SubB::printSelf.\n"<span>;
    }
}

SubA</span>::getInstance()-><span>printSelf();
SubB</span>::getInstance()->printSelf();
Salin selepas log masuk

     运行结果如下：

Stephens-<span>Air:Desktop$ php Test.php 
This is SubA::printSelf.
This is SubB::printSelf.</span>
Salin selepas log masuk

     static关键字不仅仅可以用于实例化。和self和parent一样，static还可以作为静态方法调用的标识符，甚至是从非静态上下文中调用。在该场景下，self仍然表示的是当前方法所在的类。见如下代码： 

<span>php
</span><span>abstract</span> <span>class</span><span> Base {
    </span><span>private</span> <span>$ownedGroup</span><span>;
    </span><span>public</span> <span>function</span><span> __construct() {
        </span><span>//</span><span>这里的static和上面的例子一样，表示当前调用该方法的实际类。
        //需要另外说明的是，这里的getGroup方法即便不是静态方法，也会得到相同的结果。然而倘若
        //getGroup真的只是普通类方法，那么这里还是建议使用$this。</span>
        <span>$this</span>->ownedGroup = <span>static</span>::<span>getGroup();
    }
    </span><span>public</span> <span>function</span><span> printGroup() {
        </span><span>print</span> "My Group is ".<span>$this</span>->ownedGroup."\n"<span>;
    }
    </span><span>public</span> <span>static</span> <span>function</span><span> getInstance() {
        </span><span>return</span> <span>new</span> <span>static</span><span>();
    }
    </span><span>public</span> <span>static</span> <span>function</span><span> getGroup() {
        </span><span>return</span> "default"<span>;
    }
}

</span><span>class</span> SubA <span>extends</span><span> Base {
}

</span><span>class</span> SubB <span>extends</span><span> Base {
    </span><span>public</span> <span>static</span> <span>function</span><span> getGroup() {
        </span><span>return</span> "SubB"<span>;
    }
}

SubA</span>::getInstance()-><span>printGroup();
SubB</span>::getInstance()->printGroup(); 
Salin selepas log masuk

     运行结果如下：

Stephens-<span>Air:Desktop$ php Test.php 
My Group is default
My Group is SubB</span>
Salin selepas log masuk

5. __destruct:

     析构方法的作用和构造方法__construct刚好相反，它只是在对象被垃圾收集器收集之前自动调用，我们可以利用该方法做一些必要的清理工作。

<span>php
</span><span>class</span><span> TestClass {
    </span><span>function</span><span> __destruct() {
        </span><span>print</span> "TestClass destructor is called.\n"<span>;
    }
}

</span><span>$testObj</span> = <span>new</span><span> TestClass();
</span><span>unset</span>(<span>$testObj</span><span>);
</span><span>print</span> "Application will exit.\n";
Salin selepas log masuk

     运行结果如下：

Stephens-<span>Air:Desktop$ php Test.php 
TestClass destructor is called.
Application will exit.</span>
Salin selepas log masuk

6. __clone:

     在PHP 5之后的版本中，对象之间的赋值为引用赋值，即赋值后的两个对象将指向同一地址空间，如果想基于对象赋值，可以使用PHP提供的clone方法。该方法将当前对象浅拷贝之后的副本返回，如果想在clone的过程中完成一些特殊的操作，如深拷贝，则需要在当前类的声明中实现__clone方法，该方法在执行clone的过程中会被隐式调用。另外需要格外注意的是，__clone方法是作用再被拷贝的对象上，即赋值后的对象上执行。

<span>php
</span><span>class</span><span> InnerClass {
    </span><span>public</span> <span>$id</span> = 10<span>;
    </span><span>public</span> <span>function</span><span> printSelf() {
        </span><span>print</span> '$id = '.<span>$this</span>->id."\n"<span>;
    }
}

</span><span>class</span><span> OuterClass {
    </span><span>public</span> <span>$innerClass</span><span>;
    </span><span>public</span> <span>function</span><span> __construct() {
        </span><span>$this</span>->innerClass = <span>new</span><span> InnerClass();
    }
    </span><span>public</span> <span>function</span><span> __clone() {
        </span><span>$this</span>->innerClass = <span>clone</span> <span>$this</span>-><span>innerClass;
        </span><span>print</span> "__clone is called.\n"<span>;
    }
}

</span><span>$outerA</span> = <span>new</span><span> OuterClass();
</span><span>print</span> "Before calling to clone.\n"<span>;
</span><span>$outerB</span> = <span>clone</span> <span>$outerA</span><span>;
</span><span>print</span> "After calling to clone.\n"<span>;
</span><span>$outerA</span>->innerClass->id = 20<span>;
</span><span>print</span> "In outerA: "<span>;
</span><span>$outerA</span>->innerClass-><span>printSelf();
</span><span>print</span> "In outerB: "<span>;
</span><span>$outerB</span>->innerClass->printSelf();
Salin selepas log masuk

     运行结果如下：

Stephens-<span>Air:Desktop$ php Test.php 
Before calling to clone.
__clone is called.
After calling to clone.
In outerA: $</span><span>id</span> = <span>20</span><span>
In outerB: $</span><span>id</span> = <span>10</span>
Salin selepas log masuk

7. const:

    PHP5可以在类中定义常量属性。和全局常量一样，一旦定义就不能改变。常量属性不需要像普通属性那样以$开头，按照惯例，只能用大写字母来命名常量。另外和静态属性一样，只能通过类而不能通过类的实例访问常量属性，引用常量时同样也不需要以$符号作为前导符。另外常量只能被赋值为基础类型，如整型，而不能指向任何对象类型。

<span>php
</span><span>class</span><span> TestClass {
    </span><span>const</span> AVAILABLE = 0<span>;
}

</span><span>print</span> "TestClass::AVAILABLE = ".TestClass::AVAILABLE."\n";
Salin selepas log masuk

    运行结果如下：

0Stephens-<span>Air:Desktop$ php Test.php 
TestClass::AVAILABLE </span>= <span>0</span>
Salin selepas log masuk

注：该Blog中记录的知识点，是在我学习PHP的过程中，遇到的一些PHP和其他面向对象语言相比比较特殊的地方，或者是对我本人而言确实需要簿记下来以备后查的知识点。虽然谈不上什么深度，但还是希望能与大家分享。

Label berkaitan：
co php 对象 知识点 penting 面向
sumber：php.cn
Artikel sebelumnya：[转]PHP编码规范 Artikel seterusnya：PHP内核探索之变量（6）
Kenyataan Laman Web ini
Kandungan artikel ini disumbangkan secara sukarela oleh netizen, dan hak cipta adalah milik pengarang asal. Laman web ini tidak memikul tanggungjawab undang-undang yang sepadan. Jika anda menemui sebarang kandungan yang disyaki plagiarisme atau pelanggaran, sila hubungi admin@php.cn
Artikel terbaru oleh pengarang
Isu terkini
Tatasusunan PHP yang diperoleh daripada parameter URL tidak berkelakuan seperti yang diharapkan Saya mempunyai parameter URL yang mengandungi id kategori dan saya mahu menganggapnya seba...
daripada 2024-04-06 22:09:02
0
1
1428
Di mana saya harus meletakkan arahan CustomLog dalam apache Saya menggunakan php:7.2-apachedocker. Saya perlu melumpuhkan log akses log masuk url sema...
daripada 2024-04-06 22:03:59
0
1
990
Apakah format pembolehubah dalam nilai pulangan? Saya seorang pelajar baru php. Saya menjumpai sekeping kod: if($x<time()){return[false,...
daripada 2024-04-06 21:55:20
0
1
778
Masalah yang dihadapi apabila menggunakan opentbs untuk menjana fail odt: nilai kunci yang sama dipaparkan dalam baris yang sama dan bukannya lajur yang berasingan. Saya menggunakan perpustakaan yang dipanggil OpenTbs untuk mencipta odt menggunakan PHP, s...
daripada 2024-04-06 20:18:18
0
1
483
Kumpulkan hasil MySQL mengikut ID untuk menggelung Saya mempunyai jadual dengan data penerbangan dalam mysql. Saya sedang menulis kod php yan...
daripada 2024-04-06 17:27:56
0
1
406
Topik-topik yang berkaitan
Lagi>
Cadangan popular
Tutorial Popular
Lagi>
Tutorial berkaitan
Cadangan popular
Kursus terkini
Muat turun terkini
Lagi>
kesan web
Kod sumber laman web
Bahan laman web
Templat hujung hadapan