PHP implementation example of modifying the configuration file

Let’s take a look at the installation interface of discuz, a well-known domestic forum:

If you install it here, why does it modify the config.inc.php file?

Let’s use a few simple techniques to uncover its so-called mystery!

File planning:

1.index.php -- Display modification interface

2.edit.php -- Modify function code

3.config .php -- the actual modification part

index.php displays the modification interface. Display the configuration items in config.php. Displayed in the form:

<?php

    include 'config.php';

?>


<form action="edit.php" method="post">
<input type="text" name="DB_HOST" value="<?php echo DB_HOST;?>" /><br />
<input type="text" name="DB_USER" value="<?php echo DB_USER;?>" /><br />
<input type="text" name="DB_PWD" value="<?php echo DB_PWD;?>" /><br />
<input type="text" name="DB_NAME" value="<?php echo DB_NAME;?>" /><br />


<input type="submit" value="修改" />

</form>

2.edit.php Read the config.php file and treat this file as a string. I then use regular expression matching to modify the content.

<?php

$string=file_get_contents('config.php');


//DB_HOST    localhost

foreach($_POST as $key=>$val){

   //定义正则来查找内容，这里面的key为form表单里面的name
   $yx="/define\('$key','.*?'\);/";

   //将内容匹配成对应的key和修改的值
   $re="define('$key','$val');";

   //替换内容
   $string=preg_replace($yx,$re,$string);
}


//写入成功
file_put_contents('config.php',$string);

echo '修改成功';

?>

config.php The part that actually stores the configuration file stores the real config.php file content:

<?php

define('DB_HOST','localhost');

define('DB_USER','root');

define('DB_PWD','root');

define('DB_NAME','neirong');


?>

Have you discovered that this is not as difficult as you thought. Combined with the knowledge of regular expression expressions and files, you can do it!