blocks|key|1432932|text|__construct是在PHP5中引入的，它是定义构造函数的正确方法(在PHP4中，您使用类的名称作为构造函数)。您不需要在您的类中定义构造函数，但是如果您希望传递任何关于对象构造的参数，那么您需要一个构造函数。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1432933|一个例子可能是这样的：|1432934|class+Database+{
++protected+$userName;
++protected+$password;
++protected+$dbName;

++public+function+__construct+(+$UserName,+$Password,+$DbName+)+{
++++$this->userName+=+$UserName;
++++$this->password+=+$Password;
++++$this->dbName+=+$DbName;
++}
}

//+and+you+would+use+this+as:
$db+=+new+Database+(+'user_name',+'password',+'database_name'+);|code-block|syntax|javascript|1432935|其他所有内容都在PHP手册中进行了解释：click+here|1432936|entityMap|0|LINK|mutability|MUTABLE|url|http://php.net/manual/en/language.oop5.decon.php^0|0|B|0|0|0|K|A|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Z|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|10|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|11|8|@]|D|@$9|12|A|13|1|14]]|E|$]]|$1|O|3|-4|5|6|7|15|8|@]|D|@]|E|$]]]|P|$Q|$5|R|S|T|E|$U|V]]]]

<code>__construct</code> was introduced in PHP5 and it is the right way to define your, well, constructors (in PHP4 you used the name of the class for a constructor).
You are not required to define a constructor in your class, but if you wish to pass any parameters on object construction then you need one.

An example could go like this:

<pre><code>class Database {
 protected $userName;
 protected $password;
 protected $dbName;

 public function __construct ( $UserName, $Password, $DbName ) {
 $this-&gt;userName = $UserName;
 $this-&gt;password = $Password;
 $this-&gt;dbName = $DbName;
 }
}

// and you would use this as:
$db = new Database ( 'user_name', 'password', 'database_name' );
</code></pre>

Everything else is explained in the PHP manual: <a href="http://php.net/manual/en/language.oop5.decon.php" rel="noreferrer">click here</a>

blocks|key|1647768|text|这是声明构造函数的另一种方式。您还可以使用类名，例如：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1647769|class+Cat
{
++++function+Cat()
++++{
++++++++echo+'meow';
++++}
}|code-block|syntax|javascript|1647770|和|1647771|class+Cat
{
++++function+__construct()
++++{
++++++++echo+'meow';
++++}
}|1647772|是等价的。每当创建类的新实例时，都会调用它们，在本例中，将使用下面的代码行调用它们：|1647773|$cat+=+new+Cat();|1647774|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|U|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

Its another way to declare the constructor. You can also use the class name, for ex:

<pre><code>class Cat
{
 function Cat()
 {
 echo 'meow';
 }
}
</code></pre>

and

<pre><code>class Cat
{
 function __construct()
 {
 echo 'meow';
 }
}
</code></pre>

Are equivalent. They are called whenever a new instance of the class is created, in this case, they will be called with this line:

<pre><code>$cat = new Cat();
</code></pre>

blocks|key|1647900|text|构造函数是在类实例化时自动调用的方法。这意味着构造函数的内容无需单独的方法调用即可处理。类关键字括号的内容被传递给构造函数方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1647901|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

The constructor is a method which is automatically called on class instantiation. Which means the contents of a constructor are processed without separate method calls. The contents of a the class keyword parenthesis are passed to the constructor method.

blocks|key|1648078|text|我希望这对你有所帮助：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1648079|<?php
++++//+The+code+below+creates+the+class
++++class+Person+{
++++++++//+Creating+some+properties+(variables+tied+to+an+object)
++++++++public+$isAlive+=+true;
++++++++public+$firstname;
++++++++public+$lastname;
++++++++public+$age;

++++++++//+Assigning+the+values
++++++++public+function+__construct($firstname,+$lastname,+$age)+{
++++++++++$this->firstname+=+$firstname;
++++++++++$this->lastname+=+$lastname;
++++++++++$this->age+=+$age;
++++++++}

++++++++//+Creating+a+method+(function+tied+to+an+object)
++++++++public+function+greet()+{
++++++++++return+"Hello,+my+name+is+"+.+$this->firstname+.+"+"+.+$this->lastname+.+".+Nice+to+meet+you!+:-)";
++++++++}
++++++}

++++//+Creating+a+new+person+called+"boring+12345",+who+is+12345+years+old+;-)
++++$me+=+new+Person('boring',+'12345',+12345);

++++//+Printing+out,+what+the+greet+method+returns
++++echo+$me->greet();+
++++?>|code-block|syntax|javascript|1648080|有关更多信息，请访问codecademy.com|offset|length|1648081|entityMap|0|LINK|mutability|MUTABLE|url|https://www.codecademy.com/tracks/php^0|0|0|A|E|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

I Hope this Help:

<pre><code>&lt;?php
 // The code below creates the class
 class Person {
 // Creating some properties (variables tied to an object)
 public $isAlive = true;
 public $firstname;
 public $lastname;
 public $age;

 // Assigning the values
 public function __construct($firstname, $lastname, $age) {
 $this-&gt;firstname = $firstname;
 $this-&gt;lastname = $lastname;
 $this-&gt;age = $age;
 }

 // Creating a method (function tied to an object)
 public function greet() {
 return "Hello, my name is " . $this-&gt;firstname . " " . $this-&gt;lastname . ". Nice to meet you! :-)";
 }
 }

 // Creating a new person called "boring 12345", who is 12345 years old ;-)
 $me = new Person('boring', '12345', 12345);

 // Printing out, what the greet method returns
 echo $me-&gt;greet(); 
 ?&gt;
</code></pre>

For More Information You need to Go to <a href="https://www.codecademy.com/tracks/php" rel="noreferrer">codecademy.com</a>

blocks|key|1647860|text|class+Person{
+private+$fname;
+private+$lname;

+public+function+__construct($fname,$lname){
++$this->fname+=+$fname;
++$this->lname+=+$lname;
+}
}
$objPerson1+=+new+Person('john','smith');|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1647861|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>class Person{
 private $fname;
 private $lname;

 public function __construct($fname,$lname){
 $this-&gt;fname = $fname;
 $this-&gt;lname = $lname;
 }
}
$objPerson1 = new Person('john','smith');
</code></pre>

blocks|key|1433303|text|__construct总是在创建新对象时调用，或者在初始化时调用。place.it适用于对象在使用之前可能需要的任何初始化。__construct方法是在类中执行的第一个方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1433304|++++class+Test
++++{
++++++function+__construct($value1,$value2)
++++++{
+++++++++echo+"Inside+Construct";
+++++++++echo+$this->value1;
+++++++++echo+$this->value2;
++++++}
++++}

//
++$testObject++=++new+Test('abc','123');|code-block|syntax|javascript|1433305|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

__construct is always called when creating new objects or they are invoked when initialization takes place.it is suitable for any initialization that the object may need before it is used. __construct method is the first method executed in class.

<pre><code> class Test
 {
 function __construct($value1,$value2)
 {
 echo "Inside Construct";
 echo $this-&gt;value1;
 echo $this-&gt;value2;
 }
 }

//
 $testObject = new Test('abc','123');
</code></pre>

blocks|key|1432969|text|我相信，函数__construct+()+{...}是一段可以用来替代TheActualFunctionName+()+{...}的代码，可以反复使用。如果更改了类名，则不必在代码中进行更改，因为泛型__construct总是引用实际的类name...whatever。你编写了less...or？|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1432970|entityMap^0|6|K|Z|U|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

I believe that function <code>__construct () {...}</code> is a piece of code that can be reused again and again in substitution for <code>TheActualFunctionName () {...}</code>.
If you change the CLASS Name you do not have to change within the code because the generic __construct refers always to the actual class name...whatever it is.
You code less...or?

blocks|key|1433114|text|__construct是一种在使用新对象之前对其进行初始化的方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1433115|http://php.net/manual/en/language.oop5.decon.php#object.construct|offset|length|1433116|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|1T|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@$D|O|E|P|1|Q]]|A|$]]|$1|F|3|-4|5|6|7|R|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|C]]]]

__construct is a method for initializing of new object before it is used. 
<a href="http://php.net/manual/en/language.oop5.decon.php#object.construct" rel="nofollow">http://php.net/manual/en/language.oop5.decon.php#object.construct</a>

blocks|key|1648023|text|注意:如果子类定义了一个构造函数，则父构造函数不会被隐式调用。为了运行父构造函数，需要在子构造函数中调用parent::__construct()。如果子类没有定义构造函数，那么可以从父类继承它，就像一个普通的类方法一样(如果它没有声明为private)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1648024|entityMap^0|1G|L|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

Note: Parent constructors are not called implicitly if the child class defines a constructor. In order to run a parent constructor, a call to <code>parent::__construct()</code> within the child constructor is required. If the child does not define a constructor then it may be inherited from the parent class just like a normal class method (if it was not declared as private).

blocks|key|1648206|text|__construct只是初始化一个类。假设你有以下代码；|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1648207|Class+Person+{+

+function+__construct()+{
+++echo+'Hello';
++}

}

$person+=+new+Person();

//the+result+'Hello'+will+be+shown.|code-block|syntax|javascript|1648208|我们没有创建另一个函数来回显单词“Hello”。它简单地说明了关键字__construct在初始化类或对象时非常有用。|1648209|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

__construct simply initiates a class. Suppose you have the following code;

<pre><code>Class Person { 

 function __construct() {
 echo 'Hello';
 }

}

$person = new Person();

//the result 'Hello' will be shown.
</code></pre>

We did not create another function to echo the word 'Hello'. It simply shows that the keyword __construct is quite useful in initiating a class or an object.

blocks|key|1433379|text|构造函数允许您在创建对象时初始化对象的属性。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1433380|如果您创建了一个__construct()函数，那么当您从一个类创建一个对象时，PHP将自动调用此函数。|1433381|https://www.w3schools.com/php/php_oop_constructor.asp|offset|length|1433382|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|0|1H|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|Q|8|@]|9|@$F|R|G|S|1|T]]|A|$]]|$1|H|3|-4|5|6|7|U|8|@]|9|@]|A|$]]]|I|$J|$5|K|L|M|A|$N|E]]]]

A constructor allows you to initialize an object's properties upon creation of the object.
If you create a __construct() function, PHP will automatically call this function when you create an object from a class.
<a href="https://www.w3schools.com/php/php_oop_constructor.asp" rel="nofollow noreferrer">https://www.w3schools.com/php/php_oop_constructor.asp</a>

blocks|key|1648334|text|让我先解释一下__construct()，而不是先使用这个方法。关于__construct()需要知道的一件事是，它是一个内置函数，让我在PHP中称它为方法。就像我们为过程化设计提供了print_r()一样，__construct()也是面向对象编程的内置工具。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1648335|话虽如此，让我们探索一下为什么要使用这个名为__construct()的函数。|1648336|++/*=======Class+without+__construct()========*/
++class+ThaddLawItSolution
+++{
++++++public+$description;
++++++public+$url;
++++++public+$ourServices;

++++++/*===Let+us+initialize+a+value+to+our+property+via+the+method+set_name()====+*/
+++++public+function+setName($anything,$anythingYouChoose,$anythingAgainYouChoose)
+++++{
++++++$this->description=$anything;
++++++$this->url=$anythingYouChoose;
++++++$this->ourServices=$anythingAgainYouChoose;
++++}
++++/*===Let+us+now+display+it+on+our+browser+peacefully+without+stress===*/
++++public+function+displayOnBrowser()
++++{
+++++++echo+"$this->description+is+a+technological+company+in+Nigeria+and+our+domain+name+is+actually+$this->url.Please+contact+us+today+for+our+services:$this->ourServices";
++++}
+
+}

+++++++++//Creating+an+object+of+the+class+ThaddLawItSolution
$project=new+ThaddLawItSolution;
++++++++//=======Assigning+Values+to+those+properties+via+the+method+created====//
$project->setName("Thaddlaw+IT+Solution",+"https://www.thaddlaw.com",+"Please+view+our+website");
++++++//===========Let+us+now+display+it+on+the+browser=======
$project->displayOnBrowser();|code-block|syntax|javascript|1648337|__construct()使您的工作变得非常容易，想象一下我通过该方法为这些属性赋值所花费的时间。从上面的代码中，我创建了一个对象，它是第一个，然后为第二个属性赋值，最后在浏览器上显示它。但是在创建对象(即$project=+new+ThaddLawItSolution;+)时使用__construct()时，您将执行在创建对象时立即为该方法赋值的操作。|1648338|$project=new+ThaddLawItSolution("Thaddlaw+IT+Solution",+"https://www.thaddlaw.com","Please+view+our+website");|1648339|//=现在让我们使用__constructor=====|1648340|只需删除名为setName方法并放入__construct();，然后在创建对象时立即赋值。这就是整个__construct()方法背后的要点。但请注意，这是一个内置的方法或函数|1648341|entityMap^0|7|D|Y|D|2K|9|2W|D|0|M|D|0|0|0|D|2V|X|3X|D|0|0|0|6|7|I|E|1F|D|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]|$9|Z|A|10|B|C]|$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|15|8|@$9|16|A|17|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|18|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|19|8|@$9|1A|A|1B|B|C]|$9|1C|A|1D|B|C]|$9|1E|A|1F|B|C]]|D|@]|E|$]]|$1|O|3|P|5|J|7|1G|8|@]|D|@]|E|$K|L]]|$1|Q|3|R|5|6|7|1H|8|@]|D|@]|E|$]]|$1|S|3|T|5|6|7|1I|8|@$9|1J|A|1K|B|C]|$9|1L|A|1M|B|C]|$9|1N|A|1O|B|C]]|D|@]|E|$]]|$1|U|3|-4|5|6|7|1P|8|@]|D|@]|E|$]]]|V|$]]

Let me explain <code>__construct()</code> without first using the method ... One thing to know about <code>__construct()</code> is that it is an inbuilt function, well let me call it method in PHP. Just as we have <code>print_r()</code> for procedural, the <code>__construct()</code> is an inbuilt for OOP.
That being said, let's explore why you should use this function called <code>__construct()</code>.
<pre><code> /*=======Class without __construct()========*/
 class ThaddLawItSolution
 {
 public $description;
 public $url;
 public $ourServices;

 /*===Let us initialize a value to our property via the method set_name()==== */
 public function setName($anything,$anythingYouChoose,$anythingAgainYouChoose)
 {
 $this-&gt;description=$anything;
 $this-&gt;url=$anythingYouChoose;
 $this-&gt;ourServices=$anythingAgainYouChoose;
 }
 /*===Let us now display it on our browser peacefully without stress===*/
 public function displayOnBrowser()
 {
 echo &quot;$this-&gt;description is a technological company in Nigeria and our domain name is actually $this-&gt;url.Please contact us today for our services:$this-&gt;ourServices&quot;;
 }
 
 }

 //Creating an object of the class ThaddLawItSolution
$project=new ThaddLawItSolution;
 //=======Assigning Values to those properties via the method created====//
$project-&gt;setName(&quot;Thaddlaw IT Solution&quot;, &quot;https://www.thaddlaw.com&quot;, &quot;Please view our website&quot;);
 //===========Let us now display it on the browser=======
$project-&gt;displayOnBrowser();
</code></pre>
<code>__construct()</code> makes life for you very easy, imaging the time it took me to assigning values to those properties via that method. From the code above, I created an object which is first and then assign values to the properties which is second before finally showing it on the browser. But using <code>__construct()</code> while creating an object i.e. <code>$project= new ThaddLawItSolution;</code> you would do what you did for assigning values to that method immediately while creating the object, i.e.
<pre><code>$project=new ThaddLawItSolution(&quot;Thaddlaw IT Solution&quot;, &quot;https://www.thaddlaw.com&quot;,&quot;Please view our website&quot;);
</code></pre>
//===Let's now use __constructor=====
Just remove that method called <code>setName</code> and put <code>__construct();</code> and when creating an object, you assign the values at once. That is the point behind the whole <code>__construct()</code> method. But note that this is an inbuilt method or function

I have been noticing <code>__construct</code> a lot with classes. I did a little reading and surfing the web, but I couldn't find an explanation I could understand. I am just beginning with OOP.

I was wondering if someone could give me a general idea of what it is, and then a simple example of how it is used with PHP?

What is the function __construct used for?

我已经注意到__construct在类方面的很多东西。我读了一些书，在网上冲浪，但我找不到一个我能理解的解释。我只是从OOP开始。我想知道是否有人可以给我一个大概的概念，然后是一个简单的例子如何在PHP中使用它？

问__construct使用的函数是什么？
EN

回答 12

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问__construct使用的函数是什么？
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