Fatal error: Cannot redeclare class Cause Analysis and Solution_PHP Tutorial

I use php __autoload state to automatically load classes. Today, I don’t know how a good program prompts Fatal error: Cannot redeclare class when running. It seems that the class is repeatedly defined. Let me analyze the solution below.

Error message

Fatal error: Cannot redeclare class….

It’s easy to understand from the literal point of view. It means that the class is repeatedly defined. I looked at my own code and found that it was caused by the existence of a class with the same name. Just change the class name.

Cause Analysis

1. A class with the same name is declared twice in the same file:
For example:

The code is as follows	Copy code
代码如下	复制代码
class Foo {} // some code here class Foo {} ?>

class Foo {}

// some code here

class Foo {}

?>

An error will be reported at the second Foo.

Solution: Remove the second Foo, or rename it.

代码如下	复制代码
if(class_exists('SomeClass') != true)   {      //put class SomeClass here   }  if(class_exists('SomeClass') != true) {    //put class SomeClass here }

In order to prevent repeated definitions, you can determine whether the class already exists when defining a new class:

The code is as follows

Copy code

if(class_exists('SomeClass') != true) {

代码如下	复制代码
include "some_class.php";  include "some_class.php";

//put class SomeClass here

}

if(class_exists('SomeClass') != true)

代码如下	复制代码
include "a.php";   include "some_class.php";  include "a.php"; include "some_class.php";

{

//put class SomeClass here

}

2. Repeatedly include the same class file:

For example: for a certain class file some_class.php, in a.php

The code is as follows	Copy code
include "some_class.php"; include "some_class.php";

代码如下	复制代码
class Com { } ?>

In b.php

The code is as follows	Copy code
include "a.php"; include "some_class.php"; include "a.php"; include "some_class.php";

will report an error. Solution: Replace all the above include with include_once 3. This class is a built-in class in the PHP class library. Judgment method: Write in an empty file

The code is as follows	Copy code
class Com <🎜> { <🎜> <🎜> } <🎜> ?>

At this time, it prompts Cannot redeclare class Com, indicating that this class is a built-in class in PHP. Cannot be used.

In addition, avoid using class names that are too popular, such as Com. This class may be normal in Linux but cannot run in Windows environment.

Let me remember another solution I found online. It may be useful in some situations. Remember it first

if (!class_exists('pageModule')){

The code is as follows

代码如下	复制代码
if (!class_exists('pageModule')){     require_once(PATH_site.'fileadmin/scripts/class.page.php');  }

Copy code

require_once(PATH_site.'fileadmin/scripts/class.page.php'); }

The above method does not apply to the method of using php __autoload class loading, but it can already solve the problem. __autoload is automatically loaded. We only need to find the same class name and rename it. http://www.bkjia.com/PHPjc/632073.html

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http: //www.bkjia.com/PHPjc/632073.htmlTechArticleI use php __autoload state to automatically load classes. Today’s good program does not know how to prompt when running Fatal error: Cannot redeclare class. It seems that the class is repeatedly defined. Next...