PHP 中的建構函數

php小編小新為您詳細解析PHP中的建構子。建構子是在實例化物件時自動呼叫的方法，用來初始化物件的屬性。透過建構函數，可以在建立物件時傳遞參數並對屬性進行賦值，提高程式碼的可讀性和重用性。建構函數的命名與類別名稱相同，且不需要手動調用，以便統一管理和維護程式碼。在PHP中，建構函數是物件導向程式設計的重要組成部分，深入了解並合理地應用建構函數，能夠提升程式碼的品質與效率。

我們還將使用該函數來初始化類別中具有給定參數的物件的屬性。

最後，我們將看到如何在子類別中啟動物件並在兩個類別都有單獨的建構函式時呼叫父類別建構子。

---

使用 php 建構子初始化類別中的物件的屬性

在下面的範例中，我們將建立一個類別 Student 並使用 __construct 函數為 new Student 指派其屬性。

__construct 函數減少了與使用函數 set_name() 相關的程式碼數。

<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>

輸出：

<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>

---

使用 PHP 建構子在類別中初始化 Object with Parameters 的屬性

在下面的範例程式碼中，我們建立類別 Military 並使用 __construct 函數來提供我們建立的物件的屬性和參數。

<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 &#39;Military&#39;
</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>

輸出：

<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>

---

在 PHP 中在子類別中啟動一個物件並在兩個類別都有 Individual 建構子時呼叫父類別建構子

<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>

輸出：

<code>
<code class="language-text hljs" data-lang="text"><span style="display:flex;"><span>Alice : Your Id Number is 1036398
</span></span></code></code>

Identity 類別擴展了上述程式碼中的 Student 類別。我們使用關鍵字 parent: 來呼叫 Student 類別的建構子。

以上是PHP 中的建構函數的詳細內容。更多資訊請關注PHP中文網其他相關文章！