blocks|key|314954|text|将所需的函数改为static+-+alter+class+A，这样它就有了另一个不需要任何参数的构造函数，这不是更好吗|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|314955|314956|如果一个类有一个不访问类中任何非静态属性或函数的函数，则可以将其设为静态的。|314957|class+A{
++++public+function+__construct($arg1){
++++}

++++public+static+function+foo(){
++++++++//do+something+that+doesn't+involve+the+class+properties
++++}
}|code-block|syntax|javascript|314958|然后，无需构造类即可调用它|314959|//the+constructor+will+not+be+called+as+we+haven't+created+an+instance+of+A
A::foo();|314960|静态函数和非静态函数之间的区别在于，静态函数不能访问也是静态的函数的类属性。因此，如果在foo()中有任何使用$this->的代码，则不能将其设为静态的。|style|CODE|314961|entityMap|0|LINK|mutability|MUTABLE|url|http://php.net/manual/en/language.oop5.static.php^0|8|6|0|0|0|0|0|0|0|18|5|1J|7|0^^$0|@$1|2|3|4|5|6|7|11|8|@]|9|@$A|12|B|13|1|14]]|C|$]]|$1|D|3|-4|5|6|7|15|8|@]|9|@]|C|$]]|$1|E|3|F|5|6|7|16|8|@]|9|@]|C|$]]|$1|G|3|H|5|I|7|17|8|@]|9|@]|C|$J|K]]|$1|L|3|M|5|6|7|18|8|@]|9|@]|C|$]]|$1|N|3|O|5|I|7|19|8|@]|9|@]|C|$J|K]]|$1|P|3|Q|5|6|7|1A|8|@$A|1B|B|1C|R|S]|$A|1D|B|1E|R|S]]|9|@]|C|$]]|$1|T|3|-4|5|6|7|1F|8|@]|9|@]|C|$]]]|U|$V|$5|W|X|Y|C|$Z|10]]]]

Wouldn't it be better to make the function you need <a href="http://php.net/manual/en/language.oop5.static.php" rel="nofollow noreferrer">static</a>
 - alter class A so that it has another constructor that doesn't take any aruguments

<hr>

If a class has a function that doesn't access any of the non static properties or functions in a class it can be made static.

<pre><code>class A{
 public function __construct($arg1){
 }

 public static function foo(){
 //do something that doesn't involve the class properties
 }
}
</code></pre>

It can then be called without having to construct the class

<pre><code>//the constructor will not be called as we haven't created an instance of A
A::foo();
</code></pre>

The difference between a static and a none static function is that the static function cannot access class properties of functions that are also static. So if in <code>foo()</code> you have any code that uses <code>$this-&gt;</code> you can't make it static.

blocks|key|312062|text|您可以将该方法设为静态的，并从类上下文而不是对象上下文调用它。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|312063|在代码中，它将如下所示：|312064|class+A+{
++public+static+function+func($txt)+{
++++print($txt);
++}
}

A::func('test');|code-block|syntax|javascript|312065|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

you could make the method static and call it from class context and not object context.

in code it would look like this:

<pre><code>class A {
 public static function func($txt) {
 print($txt);
 }
}

A::func('test');
</code></pre>

blocks|key|3266709|text|类构造函数将始终被调用。不过，有几种方法可以解决这个问题。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3266710|第一种方法是在构造函数中为参数提供默认值，并且仅在设置了这些参数的情况下对这些参数执行特定的操作。例如：|3266711|class+MyClass+{
++++public+__construct($file+=+null)+{
++++++++if+($file)+{
++++++++++++//+perform+whatever+actions+need+to+be+done+when+$file+IS+set
++++++++}+else+{
++++++++++++//+perform+whatever+actions+need+to+be+done+when+$file+IS+NOT+set
++++++++}
++++++++//+perform+whatever+actions+need+to+be+done+regardless+of+$file+being+set
++++}
}|code-block|syntax|javascript|3266712|另一种选择是扩展类，这样子类的构造函数就不会调用父类的构造函数。|3266713|class+MyParentClass+{
++++public+__construct($file)+{
++++++++//+perform+whatever+actions+need+to+be+done+regardless+of+$file+being+set
++++}
}

class+MyChildClass+extends+MyParentClass+{
++++public+__construct()+{
++++++++//+perform+whatever+actions+need+to+be+done+when+$file+IS+NOT+set
++++}
}|3266714|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

A classes constructor will always be called. There are a couple ways you could work around this, though.

The first way is to provide default values for your parameters in the constructor, and only perform certain actions on those parameters if they're set. For example:

<pre><code>class MyClass {
 public __construct($file = null) {
 if ($file) {
 // perform whatever actions need to be done when $file IS set
 } else {
 // perform whatever actions need to be done when $file IS NOT set
 }
 // perform whatever actions need to be done regardless of $file being set
 }
}
</code></pre>

Another option is to extend your class such that the constructor of the child class does not call the constructor of the parent class.

<pre><code>class MyParentClass {
 public __construct($file) {
 // perform whatever actions need to be done regardless of $file being set
 }
}

class MyChildClass extends MyParentClass {
 public __construct() {
 // perform whatever actions need to be done when $file IS NOT set
 }
}
</code></pre>

blocks|key|3053163|text|注意:下面的解决方案适用于PHP5.3及更低版本。从PHP5.4开始，你还可以+.|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|3053164|这确实是可能的。|3053165|从PHPUnit_Framework_MockObject_Generator修改|CODE|3053166|1++$myClass+=+unserialize(
2++++++sprintf(
3++++++++++'O:%25d:"%25s":0:{}',
4++++++++++strlen('MyClass'),+'MyClass'
5++++++)
6++);|code-block|syntax|javascript|3053167|请记住，在像PHPUnit这样的框架中，像这样的代码都是很好的，并且是合理的。但是，如果您必须在您的生产代码中包含这样的代码，那么您可能会做一些非常奇怪的事情。|3053168|3053169|既然你要求解释：|3053170|当你使用serialize+an+Object时，你会得到一个对象的字符串表示。例如|3053171|echo+serialize(new+StdClass)+//+gives+O:8:"stdClass":0:{}|3053172|O的意思是对象。8是类名的字符串长度。"stdClass"显然是类名。序列化的对象设置了0属性(稍后将详细介绍)，由空花括号表示。:只是分隔符。|3053173|可以使用unserialize函数将每个序列化的字符串重新创建为其原始的“活动”值。这样做，将绕过构造函数。正如查尔斯正确指出的那样，如果定义了magic+method+__wakeup()，就会调用它(就像序列化时调用__sleep()一样)。|3053174|在第3行，您可以看到准备与sprintf一起使用的字符串(第2行)。如您所见，类名的字符串长度为%25d，类名为%25s。这是为了告诉sprintf，它应该使用第4行传递给它的第一个参数作为数字，使用第二个参数作为字符串。因此，sprintf调用的结果是|3053175|'O:7:"MyClass":0:{}'|3053176|您可以将第4行中出现的两个"MyClass“替换为所需的类名，以便在不调用控制器的情况下创建要实例化的类的序列化字符串。|3053177|然后，绕过构造函数，将该字符串反序列化为第1行中的MyClass实例。未序列化的实例将拥有它的类的所有方法以及所有属性。如果MyClass中有属性，则这些属性将具有其默认值，除非您向序列化的虚拟字符串添加不同的值。|3053178|这已经够了。没什么太神奇的。|3053179|entityMap|0|LINK|mutability|MUTABLE|url|http://php.net/manual/en/language.oop5.serialization.php|1|http://php.net/manual/en/function.unserialize.php|2|http://php.net/manual/en/language.oop5.magic.php#language.oop5.magic.sleep^0|0|13|14|1|0|0|1|12|0|0|0|0|0|4|J|0|0|0|0|1|8|1|J|A|18|1|1T|1|0|2D|A|32|9|4|B|1|20|N|2|0|1C|2|1I|2|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|1O|8|@$9|1P|A|1Q|B|C]|$9|1R|A|1S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|1T|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|1U|8|@$9|1V|A|1W|B|J]]|D|@]|E|$]]|$1|K|3|L|5|M|7|1X|8|@]|D|@]|E|$N|O]]|$1|P|3|Q|5|6|7|1Y|8|@]|D|@]|E|$]]|$1|R|3|-4|5|6|7|1Z|8|@]|D|@]|E|$]]|$1|S|3|T|5|6|7|20|8|@]|D|@]|E|$]]|$1|U|3|V|5|6|7|21|8|@]|D|@$9|22|A|23|1|24]]|E|$]]|$1|W|3|X|5|M|7|25|8|@]|D|@]|E|$N|O]]|$1|Y|3|Z|5|6|7|26|8|@$9|27|A|28|B|J]|$9|29|A|2A|B|J]|$9|2B|A|2C|B|J]|$9|2D|A|2E|B|J]|$9|2F|A|2G|B|J]]|D|@]|E|$]]|$1|10|3|11|5|6|7|2H|8|@$9|2I|A|2J|B|J]|$9|2K|A|2L|B|J]]|D|@$9|2M|A|2N|1|2O]|$9|2P|A|2Q|1|2R]]|E|$]]|$1|12|3|13|5|6|7|2S|8|@$9|2T|A|2U|B|J]|$9|2V|A|2W|B|J]]|D|@]|E|$]]|$1|14|3|15|5|M|7|2X|8|@]|D|@]|E|$N|O]]|$1|16|3|17|5|6|7|2Y|8|@]|D|@]|E|$]]|$1|18|3|19|5|6|7|2Z|8|@]|D|@]|E|$]]|$1|1A|3|1B|5|6|7|30|8|@]|D|@]|E|$]]|$1|1C|3|-4|5|6|7|31|8|@]|D|@]|E|$]]]|1D|$1E|$5|1F|1G|1H|E|$1I|1J]]|1K|$5|1F|1G|1H|E|$1I|1L]]|1M|$5|1F|1G|1H|E|$1I|1N]]]]

Note: The solution below is for PHP 5.3 and below. As of PHP 5.4, you can also <a href="https://stackoverflow.com/a/8457580/208809">do it via Reflection as shown elsewhere on this page</a>.

This is indeed possible.

Modified from <code>PHPUnit_Framework_MockObject_Generator</code>

<pre><code>1 $myClass = unserialize(
2 sprintf(
3 'O:%d:"%s":0:{}',
4 strlen('MyClass'), 'MyClass'
5 )
6 );
</code></pre>

Please keep in mind, that code like this is all good and justified in a framework like PHPUnit. But if you have to have code like this in your production code, you are likely doing something very odd.

<hr>

Since you asked for an explanation:

When you <a href="http://php.net/manual/en/language.oop5.serialization.php" rel="nofollow noreferrer">serialize an Object</a> you get a string representation of the object. For instance

<pre><code>echo serialize(new StdClass) // gives O:8:"stdClass":0:{}
</code></pre>

The <code>O</code> means object. <code>8</code> is the string length of the class name. <code>"stdClass"</code> is obviously the class name. The serialized object has <code>0</code> properties set (more to that later), indicated by the empty curly braces. The <code>:</code> are just delimiters.

Every serialized string can be recreated into its original "live" value with the <a href="http://php.net/manual/en/function.unserialize.php" rel="nofollow noreferrer">unserialize</a> function. Doing so, will circumvent the constructor. Like Charles correctly pointed out the <a href="http://php.net/manual/en/language.oop5.magic.php#language.oop5.magic.sleep" rel="nofollow noreferrer">magic method <code>__wakeup()</code></a> will be called if it is defined (just like <code>__sleep()</code> will be called when serializing).

In Line 3 you see a string prepared to be used with sprintf (line 2). As you can see the string length of the class name is given as <code>%d</code> and the class name is given as <code>%s</code>. This is to tell sprintf that it should use the first argument passed to it in line 4 as a digit and the second as a string. Hence, the result of the sprintf call is

<pre><code>'O:7:"MyClass":0:{}'
</code></pre>

You would replace both occurences of "MyClass" in line 4 with your desired class name to create a serialized string of the class you want to instantiate without invoking the controller.

This string is then unserialized into a MyClass instance in line 1, bypassing the constructor. The unserialized instance will have all the methods of it's class and also any properties. If there is properties in MyClass, these will have their default values, unless you add different values to the serialized dummy string.

And that's already it. Nothing too magical about it.

blocks|key|315058|text|在你的情况下，我建议你考虑重新设计你的代码，这样你就不需要做这样的事情，但回答你的问题：是的，这是可能的。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|315059|你可以使用PHP5.4中引入的ReflectionClass和它的方法newInstanceWithoutConstructor，这样就可以很容易地创建一个类的实例，而不用调用它的构造函数：|315060|$reflection+=+new+ReflectionClass("ClassName");
$instance+=+$reflection->newInstanceWithoutConstructor();+//That's+it!|code-block|syntax|javascript|315061|entityMap|0|LINK|mutability|MUTABLE|url|http://www.php.net/manual/es/class.reflectionclass.php|1|http://php.net/manual/en/reflectionclass.newinstancewithoutconstructor.php^0|18|8|0|5|6|F|F|0|Z|T|1|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|@$9|10|A|11|B|C]]|D|@$9|12|A|13|1|14]|$9|15|A|16|1|17]]|E|$]]|$1|H|3|I|5|J|7|18|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|19|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]|U|$5|P|Q|R|E|$S|V]]]]

In your case I would recommend to think about redesigning your code so you don't need to do such a things, but to answer you question: yes, it is possible.

You can use <a href="http://www.php.net/manual/es/class.reflectionclass.php">ReflectionClass</a> and it's method <a href="http://php.net/manual/en/reflectionclass.newinstancewithoutconstructor.php">newInstanceWithoutConstructor</a> introduced in PHP 5.4 Then it's very easy to create an instance of a class without calling its constructor:

<pre><code>$reflection = new ReflectionClass("ClassName");
$instance = $reflection-&gt;newInstanceWithoutConstructor(); //That's it!
</code></pre>

By any means, is it possible to create an instance of an php class without calling its constructor ?

I have Class A and while creating an instance of it am passing file and in constructor of Class A am opening the file. 

Now in Class A, there is function which I need to call but am not required to pass file and so there is not need to use constructor functionality of opening file as am not passing file. 

So my question is, Is it possible by any means to create an instance of an PHP class without calling its constructor ?

Note I cannot make function static as am using some of the class properties in function.

In PHP, is it possible to create an instance of an class without calling class's constructor?

无论如何，有没有可能在不调用其构造函数的情况下创建php类的实例？我有一个A类，在创建它的一个实例时传递文件，在A类的构造函数中打开这个文件。现在在A类中，有一些函数我需要调用，但不需要传递文件，因此不需要使用打开文件的构造函数功能，因为没有传递文件。所以我的问题是，有没有可能在不调用构造函数的情况下创建PHP类的实例...

问在PHP中，可以在不调用类的构造函数的情况下创建类的实例吗？
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