Dynamic call instance analysis in php, php call instance analysis_PHP tutorial

Dynamic call instance analysis in php, php call instance analysis

The examples in this article describe the specific usage of dynamic calls in php. Share it with everyone for your reference. The specific analysis is as follows:

It is indeed a big trouble to add a lot of judgments in the program, for example:

Copy code The code is as follows:

if($fun='a'){echo "Oops!";}
elesif(){}
…
else{echo "Yeah!";}

It is really troublesome and causes huge trouble when reading and modifying the program later. At this time, we can use functions to implement each code segment to be executed, and then use a more NB method to implement these functions, and because Each function implements a function, which makes it much simpler for us to maintain.

Let’s get to the point and see what the function of dynamically calling functions in PHP is. Functions can be called dynamically in PHP. Like this $fun(), the PHP parser can call the corresponding function based on the value of the variable $fun. , for example $fun='a', the parser will see the form a();, thus calling function a, the specific code is as follows:

Copy code The code is as follows:

//controller.php
(isset($_GET['fun'])&&$_GET['fun']!='')?$fun=$_GET['fun']:$fun='def';

controller($fun);

function controller($fun){
If(function_exists($fun)) $fun();
        else echo "Function {$fun} is not defined";
}

function def(){
echo "Because the user did not pass parameters, the default function def() was called";
}
function a(){
echo "Function a is called!";
}
function b(){
echo "Function b is called!";
}
?>

The example code is as follows:

Copy code The code is as follows:

require_once showErrMsg.php;
$_action = (isset($_REQUEST[action])?$_REQUEST[action]:"");
if($_action!=null&&$_action!=){
if(function_exists($_action)){
eval("$_action();");
}else{
die(showErrMsg ( "
The method [".$_action."()] does not exist in the current php file."));
}
}
?>

function showErrMsg($strMsg){
Return "".$strMsg."";
}
?>

On the front page we can use different links to implement different functions. For example, we have such a link

http://localhost/controller.php?fun=a

When the request reaches controller.php, the PHP program will automatically execute function a().

Focus of the question:

The reason is that we first call the controller() function on the page of this program. This function first determines whether the function name defined in the parameter (the value of $fun) is defined. If it is defined, it calls this function.

If fun is not defined in the $_GET parameter: http://localhost/controller.php

Just call a default function def();

Is this code concise and correct? You can copy these codes back and see the effect for yourself - I can definitely tell you that these codes run normally!

However, I am also sorry to tell you: In fact, this seemingly neat code has a huge security risk inside it. It is a huge, huge security risk. What is it specifically? Interested friends can refer to the relevant documents. , I believe you will not use this piece of code on the server immediately?

In addition, testing has confirmed that this method can not only dynamically call functions, but also dynamically instantiate objects, like this:

Copy the code The code is as follows:

$obj = new $obj();

The code is as follows:

Copy code The code is as follows:

class A
{
Function foo()
          {
If (isset($this)) {
echo '$this is defined (';
echo get_class($this);
echo ")n";
             } else {
echo "$this is not defined.n";
            }
        }
}

class B
{
Function bar()
          {
A::foo();
                //parent::foo();
        }
}

$a = new A();
$a->foo();//Dynamic call, because the object is new
A::foo();//Static call, call directly with the class name, no new object
$b = new B();
$b->bar();//In object $b, A::foo(); makes a static call
B::bar();
?>

Summary:Static and dynamic calling both refer to the calling of methods by classes and objects. Dynamic refers to creating (new) objects and then using object variables to call methods; static calls do not create objects and directly Use the class name to call. As for another object, it is very simple. Different classes create different objects, such as class A; class B, $a = new A(); $b = new B(); $a and $b is another object relative to it.

I hope this article will be helpful to everyone’s PHP programming design.

http://www.bkjia.com/PHPjc/939411.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/939411.htmlTechArticleExample analysis of dynamic calls in php, Example analysis of php calls. The examples in this article describe the specific usage of dynamic calls in php. Share it with everyone for your reference. The specific analysis is as follows: In the program...