This article will not go into details about object-oriented knowledge. This article focuses on the constructor of PHP.
The constructor of a php class can be the magic cube __construct() or a function with the same name as the class. Examples are as follows:
<code><span><span>class</span><span>A</span>{</span><span>public</span><span><span>function</span><span>A</span><span>()</span>{</span><span>echo</span><span>'A is constructing...'</span>; } } <span><span>class</span><span>B</span>{</span><span>public</span><span><span>function</span><span>__construct</span><span>()</span>{</span><span>echo</span><span>'B is contructing...'</span>; } } <span>$a</span> = <span>new</span> A(); <span>// A is constructing...</span><span>$b</span> = <span>new</span> B(); <span>// B is constructing...</span></code>
In addition, when inheriting, you should pay attention to the following:
[The subclass does not need to write a constructor, then use the constructor of the parent class]
<code><span><span>class</span><span>A</span>{</span><span>protected</span><span>$name</span>; <span>public</span><span><span>function</span><span>A</span><span>()</span>{</span><span>echo</span><span>'A is constructing...<br>'</span>; } <span>public</span><span><span>function</span><span>set_name</span><span>(<span>$name</span>)</span>{</span><span>$this</span>->name = <span>$name</span>; } <span>public</span><span><span>function</span><span>get_name</span><span>()</span>{</span><span>return</span><span>$this</span>->name; } } <span><span>class</span><span>B</span><span>extends</span><span>A</span>{</span><span>/* public function __construct(){ echo 'B is contructing...<br>'; } */</span> } <span>//$a = new A();</span><span>$b</span> = <span>new</span> B(); <span>// A is constructing...</span><span>$b</span>->set_name(<span>'zhangsan'</span>); <span>echo</span><span>$b</span>->get_name();</code>
[If the subclass writes a constructor, the constructor of the parent class will not be called again]
<code><span><span>class</span><span>A</span>{</span><span>protected</span><span>$name</span>; <span>public</span><span><span>function</span><span>A</span><span>()</span>{</span><span>echo</span><span>'A is constructing...<br>'</span>; } <span>public</span><span><span>function</span><span>set_name</span><span>(<span>$name</span>)</span>{</span><span>$this</span>->name = <span>$name</span>; } <span>public</span><span><span>function</span><span>get_name</span><span>()</span>{</span><span>return</span><span>$this</span>->name; } } <span><span>class</span><span>B</span><span>extends</span><span>A</span>{</span><span>public</span><span><span>function</span><span>__construct</span><span>()</span>{</span><span>echo</span><span>'B is contructing...<br>'</span>; } } <span>//$a = new A();</span><span>$b</span> = <span>new</span> B(); <span>// just echo 'B is contructing...'</span><span>$b</span>->set_name(<span>'zhangsan'</span>); <span>echo</span><span>$b</span>->get_name(); <span>// zhangsan</span></code>
[ If the constructor of the parent class is private, it can be inherited, but the subclass must have its own constructor and write it clearly]
<code><span><span>class</span><span>A</span>{</span><span>protected</span><span>$name</span>; <span>private</span><span><span>function</span><span>A</span><span>()</span>{</span><span>echo</span><span>'A is constructing...<br>'</span>; } <span>public</span><span><span>function</span><span>set_name</span><span>(<span>$name</span>)</span>{</span><span>$this</span>->name = <span>$name</span>; } <span>public</span><span><span>function</span><span>get_name</span><span>()</span>{</span><span>return</span><span>$this</span>->name; } } <span><span>class</span><span>B</span><span>extends</span><span>A</span>{</span><span>public</span><span><span>function</span><span>__construct</span><span>()</span>{</span><span>echo</span><span>'B is contructing...<br>'</span>; } } <span>//$a = new A();</span><span>$b</span> = <span>new</span> B(); <span>// B is contructing...</span><span>$b</span>->set_name(<span>'zhangsan'</span>); <span>echo</span><span>$b</span>->get_name(); <span>// zhangsan</span></code>
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The above introduces the description of PHP object-oriented constructor, including the relevant content. I hope it will be helpful to friends who are interested in PHP tutorials.