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Object Clone

Object comparison

Object serialization

json

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Front-end Learning PHP - Part 5 of the Object-Oriented Series - Object Operations

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Nov 16, 2016 am 10:24 AM

[1] Object cloning [2] Object comparison [3] Object serialization [4] json

Previous words

This article mainly introduces some object operations in object-oriented

Object Clone

　Object copying, also called object cloning, can be accomplished through the clone keyword

　In most cases, we do not need to completely copy an object to obtain its properties. But there is one situation where it is really needed: if you have a window object that holds window-related resources. You may want to copy a new window, keeping all the same properties as the original window, but it must be a new object (because if it is not a new object, changes in one window will affect the other window). There is another situation: if object A stores a reference to object B, when you copy object A, and you want the object used in it to be no longer object B but a copy of B, then you must get a copy of object A.

<?<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;">$this</span>->name."，性別：".<span style="color: #800080;">$this</span>->sex."，年齡：".<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('張三','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;">$p1</span>->say();<span style="color: #008000;">//</span><span style="color: #008000;">我的名字：張三，性別：男，年齡：20</span>
    <span style="color: #800080;">$p2</span>->say();<span style="color: #008000;">//</span><span style="color: #008000;">我的名字：張三，性別：男，年齡：20</span>
?>

Object comparison

When using the comparison operator (==) to compare two object variables, the comparison principle is: if the attributes and attribute values ??of the two objects are equal, and the two objects are instances of the same class, then the two objects Variables are equal

　If you use the equality operator (===), these two object variables must point to the same instance of a certain class (that is, the same object)

<?<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>?>

Object serialization

　An object is a data type stored in memory, and its lifespan usually ends when the program that generated the object terminates. Sometimes you may need to save the state of an object and restore the object when needed. Objects record themselves by writing values ??that describe their status. This process is called serialization of objects. The object needs to be serialized in the following two situations: 1. When the object needs to be transmitted over the network, just serialize the object into a binary string; 2. When the object needs to be persisted, serialize the object and write it to a file or database.

serialize()

　Serialize() -- Serialization, returns a string containing a byte stream

unserialize()

　unserialize() -- Deserialization, can change the string back to the original object value of PHP

　Serializing an object will save all attribute variables and class name information of the object, but will not save the object’s methods

<?<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;">$a</span><span style="color: #000000;">);
  </span><span style="color: #008000;">//</span><span style="color: #008000;"> 把變量$s保存起來以便文件page2.php能夠讀到</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;">$s</span><span style="color: #000000;">);
  </span><span style="color: #008000;">//</span><span style="color: #008000;"> 現(xiàn)在可以使用對象$a里面的函數(shù) 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 ]] )

　The json_encode() method performs JSON encoding on variables

<?<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 ]]] )

　The json_decode() method decodes a JSON-formatted string, accepts a JSON-encoded string and converts it into a PHP variable. When the assoc parameter is TRUE, an array will be returned instead of an object

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

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