php editor Xiaoxin will give you a detailed analysis of the constructor in PHP. A constructor is a method that is automatically called when an object is instantiated to initialize the object's properties. Through the constructor, you can pass parameters and assign values to properties when creating an object, improving the readability and reusability of the code. The name of the constructor is the same as the class name, and there is no need to call it manually, which facilitates unified management and maintenance of the code. In PHP, constructors are an important part of object-oriented programming. In-depth understanding and rational application of constructors can improve the quality and efficiency of code.
We will also use this function to initialize the properties of the object in the class with the given parameters.
Finally, we will see how to initiate an object in a child class
and call the parent class
constructor when both classes have separate constructors.
In the following example, we will create a class Student
and assign its properties to new Student
using the __construct
function.
The __construct
function reduces the amount of code associated with using the function set_name()
.
<code> <code class="language-php hljs" data-lang="php"><span style="display:flex;"><span><span style="color:#666"><?</span>php </span></span><span style="display:flex;"><span> </span></span><span style="display:flex;"><span><span style="color:#008000;font-weight:bold">class</span> <span style="color:#00f;font-weight:bold">Student</span> { </span></span><span style="display:flex;"><span> <span style="color:#408080;font-style:italic">// Define the attributes of your class </span></span></span><span style="display:flex;"><span> </span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">public</span> <span style="color:#19177c">$name</span>; </span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">public</span> <span style="color:#19177c">$em<strong class="keylink">ai</strong>l</span>; </span></span><span style="display:flex;"><span><span style="color:#408080;font-style:italic">// Initialize the properties of the object you want to create in this class </span></span></span><span style="display:flex;"><span> </span></span><span style="display:flex;"><span><span style="color:#008000;font-weight:bold">funct<strong class="keylink">io</strong>n</span> __construct(<span style="color:#19177c">$name</span>, <span style="color:#19177c">$email</span>) { </span></span><span style="display:flex;"><span> <span style="color:#19177c">$this</span><span style="color:#666">-></span><span style="color:#7d9029">name</span> <span style="color:#666">=</span> <span style="color:#19177c">$name</span>; </span></span><span style="display:flex;"><span> <span style="color:#19177c">$this</span><span style="color:#666">-></span><span style="color:#7d9029">email</span> <span style="color:#666">=</span> <span style="color:#19177c">$email</span>; </span></span><span style="display:flex;"><span>} </span></span><span style="display:flex;"><span> </span></span><span style="display:flex;"><span><span style="color:#008000;font-weight:bold">function</span> <span style="color:#00f">get_name</span>() { </span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">return</span> <span style="color:#19177c">$this</span><span style="color:#666">-></span><span style="color:#7d9029">name</span>; </span></span><span style="display:flex;"><span>} </span></span><span style="display:flex;"><span> </span></span><span style="display:flex;"><span><span style="color:#008000;font-weight:bold">function</span> <span style="color:#00f">get_email</span>() { </span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">return</span> <span style="color:#19177c">$this</span><span style="color:#666">-></span><span style="color:#7d9029">email</span>; </span></span><span style="display:flex;"><span>} </span></span><span style="display:flex;"><span>} </span></span><span style="display:flex;"><span><span style="color:#19177c">$obj</span> <span style="color:#666">=</span> <span style="color:#008000;font-weight:bold">new</span> Student(<span style="color:#ba2121">"John"</span>, <span style="color:#ba2121">"john567@gmail.com"</span>); </span></span><span style="display:flex;"><span><span style="color:#008000;font-weight:bold">echo</span> <span style="color:#19177c">$obj</span><span style="color:#666">-></span><span style="color:#7d9029">get_name</span>(); </span></span><span style="display:flex;"><span><span style="color:#008000;font-weight:bold">echo</span> <span style="color:#ba2121">"<br>"</span>; </span></span><span style="display:flex;"><span><span style="color:#008000;font-weight:bold">echo</span> <span style="color:#19177c">$obj</span><span style="color:#666">-></span><span style="color:#7d9029">get_email</span>(); </span></span><span style="display:flex;"><span><span style="color:#bc7a00">?></span><span > </span></span></span></code></code>
Output:
<code> <code class="language-text hljs" data-lang="text"><span style="display:flex;"><span>John </span></span><span style="display:flex;"><span>john567@gmail.com </span></span></code></code>
Object with Parameters
in a class using the PHP constructor
In the example code below, we create class Military
and use the __construct
function to provide the properties and parameters of the object we create.
<code> <code class="language-php hljs" data-lang="php"><span style="display:flex;"><span><span style="color:#666"><?</span>php </span></span><span style="display:flex;"><span><span style="color:#008000;font-weight:bold">class</span> <span style="color:#00f;font-weight:bold">Military</span> { </span></span><span style="display:flex;"><span> <span style="color:#408080;font-style:italic">// Define the attributes of the class 'Military' </span></span></span><span style="display:flex;"><span> </span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">public</span> <span style="color:#19177c">$name</span>; </span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">public</span> <span style="color:#19177c">$rank</span>; </span></span><span style="display:flex;"><span> </span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">function</span> __construct(<span style="color:#19177c">$name</span>, <span style="color:#19177c">$rank</span>){ </span></span><span style="display:flex;"><span> <span style="color:#19177c">$this</span><span style="color:#666">-></span><span style="color:#7d9029">name</span> <span style="color:#666">=</span> <span style="color:#19177c">$name</span>; </span></span><span style="display:flex;"><span> <span style="color:#19177c">$this</span><span style="color:#666">-></span><span style="color:#7d9029">rank</span> <span style="color:#666">=</span> <span style="color:#19177c">$rank</span>; </span></span><span style="display:flex;"><span> } </span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">function</span> <span style="color:#00f">show_detail</span>() { </span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">echo</span> <span style="color:#19177c">$this</span><span style="color:#666">-></span><span style="color:#7d9029">name</span><span style="color:#666">.</span><span style="color:#ba2121">" : "</span>; </span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">echo</span> <span style="color:#ba2121">"Your Rank is "</span><span style="color:#666">.</span><span style="color:#19177c">$this</span><span style="color:#666">-></span><span style="color:#7d9029">rank</span><span style="color:#666">.</span><span style="color:#ba2121">"</span><span style="color:#b62;font-weight:bold">\n</span><span style="color:#ba2121">"</span>; </span></span><span style="display:flex;"><span> } </span></span><span style="display:flex;"><span>} </span></span><span style="display:flex;"><span><span style="color:#19177c">$person_obj</span> <span style="color:#666">=</span> <span style="color:#008000;font-weight:bold">new</span> Military(<span style="color:#ba2121">"Michael"</span>, <span style="color:#ba2121">"General"</span>); </span></span><span style="display:flex;"><span><span style="color:#19177c">$person_obj</span><span style="color:#666">-></span><span style="color:#7d9029">show_detail</span>(); </span></span><span style="display:flex;"><span><span style="color:#008000;font-weight:bold">echo</span> <span style="color:#ba2121">"<br>"</span>; </span></span><span style="display:flex;"><span><span style="color:#19177c">$person2</span> <span style="color:#666">=</span> <span style="color:#008000;font-weight:bold">new</span> Military(<span style="color:#ba2121">"Fred"</span>, <span style="color:#ba2121">"Commander"</span>); </span></span><span style="display:flex;"><span><span style="color:#19177c">$person2</span><span style="color:#666">-></span><span style="color:#7d9029">show_detail</span>(); </span></span><span style="display:flex;"><span><span style="color:#bc7a00">?></span><span > </span></span></span></code></code>
Output:
<code> <code class="language-text hljs" data-lang="text"><span style="display:flex;"><span>Michael : Your Rank is General </span></span><span style="display:flex;"><span>Fred : Your Rank is Commander </span></span></code></code>
when both classes have
Individual<code> <code class="language-php hljs" data-lang="php"><span style="display:flex;"><span><span style="color:#666"><?</span>php </span></span><span style="display:flex;"><span><span style="color:#008000;font-weight:bold">class</span> <span style="color:#00f;font-weight:bold">Student</span> </span></span><span style="display:flex;"><span>{ </span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">public</span> <span style="color:#19177c">$name</span>; </span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">public</span> <span style="color:#008000;font-weight:bold">function</span> __construct(<span style="color:#19177c">$name</span>) </span></span><span style="display:flex;"><span> { </span></span><span style="display:flex;"><span> <span style="color:#19177c">$this</span><span style="color:#666">-></span><span style="color:#7d9029">name</span> <span style="color:#666">=</span> <span style="color:#19177c">$name</span>; </span></span><span style="display:flex;"><span> } </span></span><span style="display:flex;"><span>}<span style="color:#008000;font-weight:bold">class</span> <span style="color:#00f;font-weight:bold">Identity</span> <span style="color:#008000;font-weight:bold">extends</span> Student </span></span><span style="display:flex;"><span>{ </span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">public</span> <span style="color:#19177c">$identity_id</span>; </span></span><span style="display:flex;"><span> </span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">public</span> <span style="color:#008000;font-weight:bold">function</span> __construct(<span style="color:#19177c">$name</span>, <span style="color:#19177c">$identity_id</span>) </span></span><span style="display:flex;"><span> { </span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">parent</span><span style="color:#666">::</span><span style="color:#7d9029">__construct</span>(<span style="color:#19177c">$name</span>); </span></span><span style="display:flex;"><span> <span style="color:#19177c">$this</span><span style="color:#666">-></span><span style="color:#7d9029">identity_id</span> <span style="color:#666">=</span> <span style="color:#19177c">$identity_id</span>; </span></span><span style="display:flex;"><span> } </span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">function</span> <span style="color:#00f">show_detail</span>() { </span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">echo</span> <span style="color:#19177c">$this</span><span style="color:#666">-></span><span style="color:#7d9029">name</span><span style="color:#666">.</span><span style="color:#ba2121">" : "</span>; </span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">echo</span> <span style="color:#ba2121">"Your Id Number is "</span><span style="color:#666">.</span><span style="color:#19177c">$this</span><span style="color:#666">-></span><span style="color:#7d9029">identity_id</span><span style="color:#666">.</span><span style="color:#ba2121">"</span><span style="color:#b62;font-weight:bold">\n</span><span style="color:#ba2121">"</span>; </span></span><span style="display:flex;"><span> } </span></span><span style="display:flex;"><span>} </span></span><span style="display:flex;"><span><span style="color:#19177c">$obj</span> <span style="color:#666">=</span> <span style="color:#008000;font-weight:bold">new</span> Identity(<span style="color:#ba2121">'Alice'</span>, <span style="color:#ba2121">'1036398'</span>); </span></span><span style="display:flex;"><span><span style="color:#008000;font-weight:bold">echo</span> <span style="color:#19177c">$obj</span><span style="color:#666">-></span><span style="color:#7d9029">show_detail</span>(); </span></span><span style="display:flex;"><span><span style="color:#bc7a00">?></span><span > </span></span></span></code></code>
Output:
<code> <code class="language-text hljs" data-lang="text"><span style="display:flex;"><span>Alice : Your Id Number is 1036398 </span></span></code></code>
The Identity
class extends the Student
class in the above code. We use the keyword parent:
to call the constructor of the Student
class.
The above is the detailed content of Constructor in PHP. For more information, please follow other related articles on the PHP Chinese website!