Instructions for dynamic calls in php_PHP tutorial

Dynamic calling is considered an advanced thing in PHP. Today we will take a look at what this advanced activity is. Let’s first analyze and determine what this dynamic calling is. Friends in need can take a look.

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

代码如下	复制代码
if($fun=’a’){echo ”哎呀！”;} elesif(){} …… else{echo “嗯！”;};

It’s 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.
You can then use a more NB method to implement these functions.
And because each function implements a function, it is much simpler for us to maintain.

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

The code is as follows	Copy code
代码如下	复制代码
//程序来源：PHP iask http://www.bkjia.com //controller.php (isset($_GET['fun'])&&$_GET['fun']!='')?$fun=$_GET['fun']:$fun='def'; controller($fun); function controller($fun){ if(function_exists($fun)) $fun(); else echo "函数{$fun}未定义"; } function def(){ echo "由于用户没有传递参数，调用了缺省的函数def()"; } function a(){ echo "函数a被调用！"; } function b(){ echo "函数b被调用！"; } ?>

//Program source: PHP iask http://www.bkjia.com

//controller.php

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

代码如下	复制代码
require_once showErrMsg.php; $_action = (isset($_REQUEST[action])?$_REQUEST[action]:""); if($_action!=null&&$_action!=){ if(function_exists($_action)){ eval("$_action();"); }else{ die(showErrMsg ( " 当前php文件中不存在方法[".$_action."()]。"));   }  } ?> function showErrMsg($strMsg){ return "".$strMsg."";  } ?>

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!";}?> Example

The code is as follows	Copy code
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 the controller .php, the PHP program will automatically execute function a().

The key point of the problem:
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

Call a default function def();

Is this code like this? Is it right to be concise? 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, a huge, huge security risk! Let’s talk about what it is specifically, “About the Security Issues of Dynamic Calling Functions in PHP” which will be released on time at 10 o’clock tomorrow. You will definitely not use this piece of code on the server immediately, right?

In addition, testing has confirmed that this method can not only dynamically call functions, but also dynamically instantiate objects, like this: $obj = new $obj();

{

The code is as follows

代码如下	复制代码
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();//动态调用，因为new了对象 A::foo();//静态调用，直接用类名去调用，没有new对象 $b = new B(); $b->bar();//在对象$b中，A::foo();进行静态调用 B::bar(); ?>

Copy code

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, use it directly Class name to call, there is no new object $b = new B();$b->bar();//In object $b, A::foo(); makes a static callB::bar();?> Summary: Static and dynamic calls refer to the calls of classes and objects to their methods. Dynamic refers to creating (new) the object and then using the object variable to call the method; static means not creating the object and calling it directly using the class name. As for another object, it’s very simple. Different classes create different objects, such as class A; class B, $a = new A(); $b = new B(); $a and $b are relative to each other. Another object. http://www.bkjia.com/PHPjc/444729.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/444729.htmlTechArticleDynamic calling is considered an advanced thing in PHP. Today we will take a look at what this advanced job is. First Let’s analyze and determine what this dynamic call is. Friends in need can take a look. ...