How to access private properties of a class from outside a class in PHP

We all know that the private properties of a class are not accessible outside the class, including in subclasses. For example, the following code:

<code><span><span><?php</span>  
<span>class</span> Example1{ 
    <span>private</span> <span>$</span><span>_prop</span> = <span>'test'</span>; 
} 
 
<span>$</span><span>r</span> = <span>function</span>(Example1 <span>$</span><span>e</span>){ 
    <span>return</span> <span>$</span><span>e</span>->_prop; 
}; 
 
<span>$</span><span>a</span> = <span>new</span> Example1(); 
var_dump(<span>$</span><span>r</span>(<span>$</span><span>a</span>)); 
 
<span>//运行结果：Fatal error: Cannot access private property Example1::$_prop</span> 
<span>?></span> 
</span></span></code>

But in some cases we need to access the private properties of the class. There are several methods to achieve this:

1. Use reflection

<code><span><span><?php</span>  
<span>class</span> Example1{ 
    <span>private</span> <span>$</span><span>_prop</span> = <span>'test'</span>; 
} 
 
<span>$</span><span>r</span> = <span>function</span>(Example1 <span>$</span><span>e</span>){ 
    <span>return</span> <span>$</span><span>e</span>->_prop; 
}; 
 
<span>$</span><span>a</span> = <span>new</span> Example1(); 
<span>$</span><span>rfp</span> = <span>new</span> ReflectionProperty(<span>'Example1'</span>,<span>'_prop'</span>); 
<span>$</span><span>rfp</span>->setAccessible(<span>true</span>); 
var_dump(<span>$</span><span>rfp</span>->getValue(<span>$</span><span>a</span>)); 
 
<span>//结果输出：string 'test' (length=4)</span> 
<span>?></span> 
</span></span></code>

2. Use Closure::bind()
This The method is new in PHP 5.4.0.

<code><span><span><?php</span>  
<span>class</span> Example1{ 
    <span>private</span> <span>$</span><span>_prop</span> = <span>'test'</span>; 
} 
 
<span>$</span><span>r</span> = <span>function</span>(Example1 <span>$</span><span>e</span>){ 
    <span>return</span> <span>$</span><span>e</span>->_prop; 
}; 
 
<span>$</span><span>a</span> = <span>new</span> Example1(); 
<span>$</span><span>r</span> = Closure::bind(<span>$</span><span>r</span>,<span>null</span>,<span>$</span><span>a</span>); 
 
var_dump(<span>$</span><span>r</span>(<span>$</span><span>a</span>)); 
 
<span>//结果输出：string 'test' (length=4)</span> 
<span>?></span> 
</span></span></code>

In addition, we can also access by reference, so that we can modify the private properties of the class:

<code><span><span><?php</span>  
<span>class</span> Example1{ 
    <span>private</span> <span>$</span><span>_prop</span> = <span>'test'</span>; 
} 
 
<span>$</span><span>a</span> = <span>new</span> Example1(); 
<span>$</span><span>r</span> = Closure::bind(<span>function</span> & (Example1 <span>$</span><span>e</span>) { 
    <span>return</span> <span>$</span><span>e</span>->_prop; 
}, <span>null</span>, <span>$</span><span>a</span>); 
 
<span>$</span><span>cake</span> = & <span>$</span><span>r</span>(<span>$</span><span>a</span>); 
<span>$</span><span>cake</span> = <span>'lie'</span>; 
var_dump(<span>$</span><span>r</span>(<span>$</span><span>a</span>)); 
 
<span>//结果输出：string 'lie' (length=3)</span> 
</span></span></code>

According to this, we can encapsulate a function to read/set the private properties of the class:

<code><span><span><?php</span> 
<span>$</span><span>reader</span> = <span>function</span> & (<span>$</span><span>object</span>, <span>$</span><span>property</span>) { 
    <span>$</span><span>value</span> = & Closure::bind(<span>function</span> & () <span>use</span> (<span>$</span><span>property</span>) { 
        <span>return</span> <span>$</span><span>this</span>-><span>$</span><span>property</span>; 
    }, <span>$</span><span>object</span>, <span>$</span><span>object</span>)->__invoke(); 
 
    <span>return</span> <span>$</span><span>value</span>; 
}; 
<span>?></span> 
</span></span></code>

Closure ::bind() is also very useful. We can use this feature to dynamically add methods to a class. The official documentation gives an example:

<code><span><span><?php</span> 
trait MetaTrait 
{ 
     
    <span>private</span> <span>$</span><span>methods</span> = <span>array</span>(); 
     
    <span>public</span> <span>function</span> addMethod(<span>$</span><span>methodName</span>, <span>$</span><span>methodCallable</span>) 
    { 
        <span>if</span> (!is_callable(<span>$</span><span>methodCallable</span>)) { 
            <span>throw</span> <span>new</span> InvalidArgumentException(<span>'Second param must be callable'</span>); 
        } 
        <span>$</span><span>this</span>->methods[<span>$</span><span>methodName</span>] = Closure::bind(<span>$</span><span>methodCallable</span>, <span>$</span><span>this</span>, get_class()); 
    } 
     
    <span>public</span> <span>function</span> __call(<span>$</span><span>methodName</span>, <span>array</span> <span>$</span><span>args</span>) 
    { 
        <span>if</span> (<span>isset</span>(<span>$</span><span>this</span>->methods[<span>$</span><span>methodName</span>])) { 
            <span>return</span> call_user_func_array(<span>$</span><span>this</span>->methods[<span>$</span><span>methodName</span>], <span>$</span><span>args</span>); 
        } 
         
        <span>throw</span> RunTimeException(<span>'There is no method with the given name to call'</span>); 
    } 
     
} 
 
<span>class</span> HackThursday { 
    <span>use</span> MetaTrait; 
     
    <span>private</span> <span>$</span><span>dayOfWeek</span> = <span>'Thursday'</span>; 
     
} 
 
<span>$</span><span>test</span> = <span>new</span> HackThursday(); 
<span>$</span><span>test</span>->addMethod(<span>"addedMethod"</span>,<span>function</span>(){ 
    <span>return</span> <span>'我是被动态添加进来的方法'</span>; 
}); 
 
<span>echo</span> <span>$</span><span>test</span>->addedMethod(); 
 
<span>//结果输出：我是被动态添加进来的方法</span> 
<span>?></span></span></span></code>

The above introduces the method of externally accessing the private properties of a class in PHP, including the relevant content. I hope it will be helpful to friends who are interested in PHP tutorials.