A brief analysis of the application of PHP 5 clone function_PHP tutorial

There is no doubt that the launch of PHP5 has had far-reaching significance for the development of web applications. This is not just because of its high degree of backward compatibility with PHP4.

Of course, the PHP5 data package has a powerful object model and a complete set of new functions and libraries, not to mention its portable exception mechanism, which gives it the ability to effectively handle errors and exceptions. Writing to a file on the server via PHP

Of course, when we use the word "function", we are not talking about just the usual meaning of performing a specified task such as reading data from a file or The concept of applying a filter to a supplied variable). We also refer to some magic functions (such as PHP 5's clone function), that is, functions that do not have a default execution task and can be automatically called by the PHP engine in response to certain events.

When developing object-oriented PHP applications, the _set(), _get() and _call() methods are typical representatives of magic functions, but there are other magic functions that deserve in-depth analysis by developers. In this article, we will focus on the “_clone()” method, which, as the name suggests, can be called from behind the scenes using the “clone” PHP keyword.

Trigger the function from behind the scenes when copying the object

As we mentioned before, when using the clone keyword, the _clone() function (clone function) will be automatically invoked. For the sake of brevity, now we only talk about the clone keyword used to create a separate copy of the specified object, not about creating a reference. Add HTML to multiple files using PHP

Now, return the _clone function to give it a clear task instruction. To achieve this, let's look at the following code:

<ol class="dp-c">
<li class="alt"><span><span> </span><span class="keyword">class</span><span> User   </span></span></li>
<li><span>{  </span></li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="comment">// constructor (not implemented) </span><span> </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="keyword">public</span><span> </span><span class="keyword">function</span><span> _construct(){}  </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="comment">// set undeclared property in a restrictive way </span><span> </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="keyword">public</span><span> </span><span class="keyword">function</span><span> __set(</span><span class="vars">$property</span><span>, </span><span class="vars">$value</span><span>)  </span>
</li>
<li class="alt"><span> </span></li>
<li><span>{  </span></li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="keyword">if</span><span> (in_array(</span><span class="vars">$property</span><span>, </span><span class="keyword">array</span><span>(</span><span class="string">'fname'</span><span>, </span><span class="string">'lname'</span><span>, </span><span class="string">'email'</span><span>)) === TRUE)  </span>
</li>
<li class="alt"><span> </span></li>
<li><span>{  </span></li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="vars">$this</span><span>-></span><span class="vars">$property</span><span> = </span><span class="vars">$value</span><span>;  </span>
</li>
<li class="alt"><span> </span></li>
<li><span>}  </span></li>
<li class="alt"><span> </span></li>
<li><span>}  </span></li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="comment">// get undeclared property </span><span> </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="keyword">public</span><span> </span><span class="keyword">function</span><span> __get(</span><span class="vars">$property</span><span>)  </span>
</li>
<li class="alt"><span> </span></li>
<li><span>{  </span></li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="keyword">if</span><span> (isset(</span><span class="vars">$this</span><span>-></span><span class="vars">$property</span><span>))  </span>
</li>
<li class="alt"><span> </span></li>
<li><span>{  </span></li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="keyword">return</span><span> </span><span class="vars">$this</span><span>-></span><span class="vars">$property</span><span>;  </span>
</li>
<li class="alt"><span> </span></li>
<li><span>}  </span></li>
<li class="alt"><span> </span></li>
<li><span>}  </span></li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="comment">// single point to fetch user data </span><span> </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="keyword">public</span><span> </span><span class="keyword">function</span><span> __call(</span><span class="vars">$method</span><span>, </span><span class="vars">$args</span><span>)  </span>
</li>
<li class="alt"><span> </span></li>
<li><span>{  </span></li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="keyword">if</span><span> (</span><span class="vars">$method</span><span> === </span><span class="string">'fetch'</span><span> AND </span><span class="func">empty</span><span class="keyword">empty</span><span>(</span><span class="vars">$args</span><span>) === FALSE)  </span>
</li>
<li class="alt"><span> </span></li>
<li><span>{  </span></li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="keyword">return</span><span> </span><span class="vars">$this</span><span>-></span><span class="vars">$args</span><span>[0];  </span>
</li>
<li class="alt"><span> </span></li>
<li><span>}  </span></li>
<li class="alt"><span> </span></li>
<li><span>}  </span></li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="comment">// implement __clone( method </span><span> </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="keyword">public</span><span> </span><span class="keyword">function</span><span> __clone()  </span>
</li>
<li class="alt"><span> </span></li>
<li><span>{  </span></li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="func">echo</span><span> </span><span class="string">'Cloning user object.'</span><span>;  </span>
</li>
<li class="alt"><span> </span></li>
<li><span>}  </span></li>
<li class="alt"><span> </span></li>
<li><span>} </span></li>
</ol>

In this particular example, we are going to give the above _clone method a less obvious task to help you understand better, But trust that this function can be used to perform more complex tasks. No matter how simple the _clone function demonstrated in this article is, when copying a simple User class instance, this function is very helpful in showing us how the PHP engine calls functions.

Calling the Clone method when copying an object

The best way to understand how the PHP interpreter calls the _clone() function is to watch a demonstration of how to copy a simple User Concrete examples of class instances.

We made a small script that uses the clone keyword in the clone function to copy a user object to trigger a call to the _clone() method. The script is defined as follows:

<ol class="dp-c">
<li class="alt"><span><span>  </span><span class="vars">$user</span><span> = </span><span class="keyword">new</span><span> User();   </span></span></li>
<li>
<span></span><span class="vars">$user</span><span>->fname = </span><span class="string">'Alejandro'</span><span>;  </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="vars">$user</span><span>->lname = </span><span class="string">'Gervasio'</span><span>;  </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="vars">$user</span><span>->email = </span><span class="string">'alejandro@mydomain.com'</span><span>;  </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="comment">// display user data </span><span> </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="func">echo</span><span> </span><span class="string">'First Name : '</span><span> . </span><span class="vars">$user</span><span>->fetch(</span><span class="string">'fname'</span><span>) . </span><span class="string">' Last Name : '</span><span> . </span><span class="vars">$user</span><span>->fetch(</span><span class="string">'lname'</span><span>) .<br></span><span class="string">' Email : '</span><span> . </span><span class="vars">$user</span><span>->fetch(</span><span class="string">'email'</span><span>);  </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="comment">/* </span> </li>
<li class="alt"><span> </span></li>
<li><span><span class="comment">displays the following </span> </span></li>
<li class="alt"><span> </span></li>
<li><span><span class="comment">First Name : Alejandro Last Name : Gervasio Email : alejandro@mydomain.com </span> </span></li>
<li class="alt"><span> </span></li>
<li><span><span class="comment">*/</span><span> </span></span></li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="comment">// clone user object </span><span> </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="vars">$newuser</span><span> = clone </span><span class="vars">$user</span><span>;  </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span></span><span class="comment">/* </span> </li>
<li class="alt"><span> </span></li>
<li><span><span class="comment">displays the following </span> </span></li>
<li class="alt"><span> </span></li>
<li><span><span class="comment">Cloning user object. </span> </span></li>
<li class="alt"><span> </span></li>
<li><span><span class="comment">*/</span><span> </span></span></li>
</ol>

This code is easy to write and easy to understand. As you can see, once the script generates an object in the User class and creates some undeclared properties, it copies the object. This process will automatically call the relevant _clone() method.

This specific approach supports the execution of more complex and beneficial tasks. So, if these amazing functions that come with PHP5 have caught your attention, you might want to improve your programming skills by using them. Such an attempt would be extremely illuminating.

Conclusion

In this article, we discussed how to implement and use the _clone() function. This function is automatically referenced when an object is copied via the clone keyword; this is the power of the PHP 5 clone function.

http://www.bkjia.com/PHPjc/446617.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/446617.htmlTechArticleThere is no doubt that the launch of PHP5 has had far-reaching significance for the development of network applications. This is not just because of its high degree of backward compatibility with PHP4. Of course, the PHP5 data package has powerful...