前端学PHP之面向对象系列第五篇对象操作-php手册-PHP中文网

前面的话

　　本文主要介绍面向对象中的一些对象操作

对象克隆

　　对象复制，又叫对象克隆，可以通过 clone 关键字来完成

　　在多数情况下，我们并不需要完全复制一个对象来获得其中属性。但有一个情况下确实需要：如果你有一个窗口对象，该对象持有窗口相关的资源。你可能会想复制一个新的窗口，保持所有属性与原来的窗口相同，但必须是一个新的对象（因为如果不是新的对象，那么一个窗口中的改变就会影响到另一个窗口）。还有一种情况：如果对象 A 中保存着对象 B 的引用，当你复制对象A时，你想其中使用的对象不再是对象 B 而是 B 的一个副本，那么你必须得到对象 A 的一个副本

<span style="color: #000000;">php
    </span><span style="color: #0000ff;">class</span><span style="color: #000000;"> Person{
        </span><span style="color: #0000ff;">private</span> <span style="color: #800080;">$name</span><span style="color: #000000;">;
        </span><span style="color: #0000ff;">private</span> <span style="color: #800080;">$sex</span><span style="color: #000000;">;
        </span><span style="color: #0000ff;">private</span> <span style="color: #800080;">$age</span><span style="color: #000000;">;
        </span><span style="color: #0000ff;">function</span> __construct(<span style="color: #800080;">$name</span>="",<span style="color: #800080;">$sex</span>="",<span style="color: #800080;">$age</span>=1<span style="color: #000000;">){
            </span><span style="color: #800080;">$this</span>->name= <span style="color: #800080;">$name</span><span style="color: #000000;">;
            </span><span style="color: #800080;">$this</span>->sex = <span style="color: #800080;">$sex</span><span style="color: #000000;">;
            </span><span style="color: #800080;">$this</span>->age = <span style="color: #800080;">$age</span><span style="color: #000000;">;
        }
        </span><span style="color: #0000ff;">function</span><span style="color: #000000;"> say(){
            </span><span style="color: #0000ff;">echo</span> "我的名字：" .<span style="color: #800080;">$this</span>->name."，性别：".<span style="color: #800080;">$this</span>->sex."，年龄：".<span style="color: #800080;">$this</span>->age."<br>"<span style="color: #000000;">;
        }
    }
    </span><span style="color: #800080;">$p1</span> = <span style="color: #0000ff;">new</span> Person('张三','男','20'<span style="color: #000000;">);
    </span><span style="color: #800080;">$p2</span> = <span style="color: #0000ff;">clone</span> <span style="color: #800080;">$p1</span><span style="color: #000000;">;
    </span><span style="color: #800080;">$p1</span>->say();<span style="color: #008000;">//</span><span style="color: #008000;">我的名字：张三，性别：男，年龄：20</span>
    <span style="color: #800080;">$p2</span>->say();<span style="color: #008000;">//</span><span style="color: #008000;">我的名字：张三，性别：男，年龄：20</span>
?>

对象比较

　　当使用比较运算符（==）比较两个对象变量时，比较的原则是：如果两个对象的属性和属性值都相等，而且两个对象是同一个类的实例，那么这两个对象变量相等

　　而如果使用全等运算符（===），这两个对象变量一定要指向某个类的同一个实例（即同一个对象）

<span style="color: #000000;">php
</span><span style="color: #0000ff;">function</span> bool2str(<span style="color: #800080;">$bool</span><span style="color: #000000;">)
{
    </span><span style="color: #0000ff;">if</span> (<span style="color: #800080;">$bool</span> === <span style="color: #0000ff;">false</span><span style="color: #000000;">) {
        </span><span style="color: #0000ff;">return</span> 'FALSE'<span style="color: #000000;">;
    } </span><span style="color: #0000ff;">else</span><span style="color: #000000;"> {
        </span><span style="color: #0000ff;">return</span> 'TRUE'<span style="color: #000000;">;
    }
}
</span><span style="color: #0000ff;">function</span> compareObjects(&<span style="color: #800080;">$o1</span>, &<span style="color: #800080;">$o2</span><span style="color: #000000;">)
{
    </span><span style="color: #0000ff;">echo</span> 'o1 == o2 : ' . bool2str(<span style="color: #800080;">$o1</span> == <span style="color: #800080;">$o2</span>) . "\n"<span style="color: #000000;">;
    </span><span style="color: #0000ff;">echo</span> 'o1 != o2 : ' . bool2str(<span style="color: #800080;">$o1</span> != <span style="color: #800080;">$o2</span>) . "\n"<span style="color: #000000;">;
    </span><span style="color: #0000ff;">echo</span> 'o1 === o2 : ' . bool2str(<span style="color: #800080;">$o1</span> === <span style="color: #800080;">$o2</span>) . "\n"<span style="color: #000000;">;
    </span><span style="color: #0000ff;">echo</span> 'o1 !== o2 : ' . bool2str(<span style="color: #800080;">$o1</span> !== <span style="color: #800080;">$o2</span>) . "\n"<span style="color: #000000;">;
}
</span><span style="color: #0000ff;">class</span><span style="color: #000000;"> Flag
{
    </span><span style="color: #0000ff;">public</span> <span style="color: #800080;">$flag</span><span style="color: #000000;">;
    </span><span style="color: #0000ff;">function</span> Flag(<span style="color: #800080;">$flag</span> = <span style="color: #0000ff;">true</span><span style="color: #000000;">) {
        </span><span style="color: #800080;">$this</span>->flag = <span style="color: #800080;">$flag</span><span style="color: #000000;">;
    }
}
</span><span style="color: #0000ff;">class</span><span style="color: #000000;"> OtherFlag
{
    </span><span style="color: #0000ff;">public</span> <span style="color: #800080;">$flag</span><span style="color: #000000;">;
    </span><span style="color: #0000ff;">function</span> OtherFlag(<span style="color: #800080;">$flag</span> = <span style="color: #0000ff;">true</span><span style="color: #000000;">) {
        </span><span style="color: #800080;">$this</span>->flag = <span style="color: #800080;">$flag</span><span style="color: #000000;">;
    }
}

</span><span style="color: #800080;">$o</span> = <span style="color: #0000ff;">new</span><span style="color: #000000;"> Flag();
</span><span style="color: #800080;">$p</span> = <span style="color: #0000ff;">new</span><span style="color: #000000;"> Flag();
</span><span style="color: #800080;">$q</span> = <span style="color: #800080;">$o</span><span style="color: #000000;">;
</span><span style="color: #800080;">$r</span> = <span style="color: #0000ff;">new</span><span style="color: #000000;"> OtherFlag();
</span><span style="color: #008000;">/*</span><span style="color: #008000;">
Two instances of the same class
o1 == o2 : TRUE
o1 != o2 : FALSE
o1 === o2 : FALSE
o1 !== o2 : TRUE
 </span><span style="color: #008000;">*/</span>
<span style="color: #0000ff;">echo</span> "Two instances of the same class\n"<span style="color: #000000;">;
compareObjects(</span><span style="color: #800080;">$o</span>, <span style="color: #800080;">$p</span><span style="color: #000000;">);
</span><span style="color: #008000;">/*</span><span style="color: #008000;">
Two references to the same instance
o1 == o2 : TRUE
o1 != o2 : FALSE
o1 === o2 : TRUE
o1 !== o2 : FALSE
 </span><span style="color: #008000;">*/</span>
<span style="color: #0000ff;">echo</span> "\nTwo references to the same instance\n"<span style="color: #000000;">;
compareObjects(</span><span style="color: #800080;">$o</span>, <span style="color: #800080;">$q</span><span style="color: #000000;">);
</span><span style="color: #008000;">/*</span><span style="color: #008000;">
Instances of two different classes
o1 == o2 : FALSE
o1 != o2 : TRUE
o1 === o2 : FALSE
o1 !== o2 : TRUE
 </span><span style="color: #008000;">*/</span>
<span style="color: #0000ff;">echo</span> "\nInstances of two different classes\n"<span style="color: #000000;">;
compareObjects(</span><span style="color: #800080;">$o</span>, <span style="color: #800080;">$r</span><span style="color: #000000;">);
</span>?>

对象串行化

　　对象是一种在内存中存储的数据类型，它的寿命通常随着生成该对象的程序终止而终止。有时候可能需要将对象的状态保存下来，需要时再将对象恢复。对象通过写出描述自己状态的数值来记录自己，这个过程称对象的串行化（Serialization）。以下两种情况需要将对象串行化：1、对象需要在网络中传输时，将对象串行化成二进制串即可；2、对象需要持久保存时，将对象串行化后写入文件或数据库

serialize()

　　serialize() -- 串行化，返回一个包含字节流的字符串

unserialize()

　　unserialize() -- 反串行化，能够重新把字符串变回php原来的对象值

　　串行化一个对象将会保存对象的所有属性变量和类名信息，但是不会保存对象的方法

<span style="color: #000000;">php
</span><span style="color: #008000;">//</span><span style="color: #008000;"> classa.inc:</span>
  <span style="color: #0000ff;">class</span><span style="color: #000000;"> A {
      </span><span style="color: #0000ff;">public</span> <span style="color: #800080;">$one</span> = 1<span style="color: #000000;">;
      </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">function</span><span style="color: #000000;"> show_one() {
          </span><span style="color: #0000ff;">echo</span> <span style="color: #800080;">$this</span>-><span style="color: #000000;">one;
      }
  }
  
</span><span style="color: #008000;">//</span><span style="color: #008000;"> page1.php:</span>
  <span style="color: #0000ff;">include</span>("classa.inc"<span style="color: #000000;">);
  </span><span style="color: #800080;">$a</span> = <span style="color: #0000ff;">new</span><span style="color: #000000;"> A;
  </span><span style="color: #800080;">$s</span> = <span style="color: #008080;">serialize</span>(<span style="color: #800080;">$a</span><span style="color: #000000;">);
  </span><span style="color: #008000;">//</span><span style="color: #008000;"> 把变量$s保存起来以便文件page2.php能够读到</span>
  <span style="color: #008080;">file_put_contents</span>('store', <span style="color: #800080;">$s</span><span style="color: #000000;">);

</span><span style="color: #008000;">//</span><span style="color: #008000;"> page2.php:</span>
  <span style="color: #0000ff;">include</span>("classa.inc"<span style="color: #000000;">);
  </span><span style="color: #800080;">$s</span> = <span style="color: #008080;">file_get_contents</span>('store'<span style="color: #000000;">);
  </span><span style="color: #800080;">$a</span> = <span style="color: #008080;">unserialize</span>(<span style="color: #800080;">$s</span><span style="color: #000000;">);
  </span><span style="color: #008000;">//</span><span style="color: #008000;"> 现在可以使用对象$a里面的函数 show_one()</span>
  <span style="color: #800080;">$a</span>-><span style="color: #000000;">show_one();
</span>?>

json

json_encode

<span style="color: #0000ff;">string</span> json_encode ( <span style="color: #0000ff;">mixed</span> <span style="color: #800080;">$value</span> [, int <span style="color: #800080;">$options</span> = 0 [, int <span style="color: #800080;">$depth</span> = 512 ]] )

　　json_encode()方法对变量进行 JSON 编码

<span style="color: #000000;">php
</span><span style="color: #800080;">$arr</span> = <span style="color: #0000ff;">array</span> ('a'=>1,'b'=>2,'c'=>3,'d'=>4,'e'=>5<span style="color: #000000;">);
</span><span style="color: #0000ff;">echo</span> json_encode(<span style="color: #800080;">$arr</span>);<span style="color: #008000;">//</span><span style="color: #008000;">{"a":1,"b":2,"c":3,"d":4,"e":5}</span>
?>

json_decode

<span style="color: #0000ff;">mixed</span> json_decode ( <span style="color: #0000ff;">string</span> <span style="color: #800080;">$json</span> [, bool <span style="color: #800080;">$assoc</span> = <span style="color: #0000ff;">false</span> [, int <span style="color: #800080;">$depth</span> = 512 [, int <span style="color: #800080;">$options</span> = 0 ]]] )

　　json_decode()方法对 JSON 格式的字符串进行解码，接受一个 JSON 编码的字符串并且把它转换为 PHP 变量，当assoc参数为 TRUE 时，将返回 array 而非 object

<span style="color: #000000;">php
</span><span style="color: #800080;">$json</span> = '{"a":1,"b":2,"c":3,"d":4,"e":5}'<span style="color: #000000;">;
</span><span style="color: #008000;">/*</span><span style="color: #008000;">
object(stdClass)#1 (5) {
    ["a"] => int(1)
    ["b"] => int(2)
    ["c"] => int(3)
    ["d"] => int(4)
    ["e"] => int(5)
}
 </span><span style="color: #008000;">*/</span>
<span style="color: #008080;">var_dump</span>(json_decode(<span style="color: #800080;">$json</span><span style="color: #000000;">));

</span><span style="color: #008000;">/*</span><span style="color: #008000;">
array(5) {
    ["a"] => int(1)
    ["b"] => int(2)
    ["c"] => int(3)
    ["d"] => int(4)
    ["e"] => int(5)
}
 </span><span style="color: #008000;">*/</span>
<span style="color: #008080;">var_dump</span>(json_decode(<span style="color: #800080;">$json</span>, <span style="color: #0000ff;">true</span><span style="color: #000000;">));
</span>?>