What is htmlspecialchars ($_ server php_self?
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If you want a form to be handled by the same URL that is used to display it, always use As you've already figured out, there are serious risks
of cross-site scripting (XSS) if you use either of the In this article shows the usage of PHP_SELF variable and how to avoid PHP_SELF exploits. What is PHP_SELF variable?PHP_SELF is a variable that returns the current script being executed. This variable returns the name and path of the current file (from the root folder). You can use this variable in the action field of the FORM. There are also certain exploits that you need to be aware of. We shall discuss all these points in this article.
We will now see some examples. a) Suppose your php file is located at the address: In this case, PHP_SELF will contain: b) Suppose your php file is located at the address: For this URL, PHP_SELF will be : Using the PHP_SELF variable in the action field of the formA common use of PHP_SELF variable is in the action field of the However, if you provide the name of the file in the action field, in case you happened to rename the file, you need to update the action field as well; or your forms will stop working. Using PHP_SELF variable you can write more generic code which can be used on any page and you do not need to edit the action field. Consider, you have a file called form-action.php and want to load the same page after the form is submitted. The usual form code will be:
We can use the PHP_SELF variable instead of “form-action.php”. The code becomes:
The complete code of “form-action.php”Here is the combined code, that contains both the form and the PHP script.
This PHP code is above the HTML
part and will be executed first. The first line of code is checking if the form is submitted or not. The name of the submit button is “submit”. When the submit button is pressed the If the form is not submitted the IF condition will be FALSE as there will be no values in What are PHP_SELF exploits and how to avoid themThe PHP_SELF variable is used to get the name and path of the current file but it can be used by the hackers too. If PHP_SELF is used in your page then a user can enter a slash (/) and then some Cross Site Scripting (XSS) commands to execute. See below for an example:
Now, if a user has entered the normal URL in the address bar like
This is the normal case. Now consider that the user has called this script by entering the following URL in the browser's address bar:
In this case, after PHP processing the code becomes:
You can see that this code has added a script tag and an alert command. When this page is be loaded, user will see an alert box. This is just a simple example how the PHP_SELF variable can be exploited. Any
JavaScript code can be added between the “script” tag. How to Avoid the PHP_SELF exploitsPHP_SELF exploits can be avoided by using the htmlentities() function. For example, the form code should be like this to avoid the PHP_SELF exploits:
The htmlentities() function encodes the HTML entities. Now if the user tries to exploit the PHP_SELF variable, the attempt will fail and the result of entering malicious code in URL will result in the following output:
As you can see, the script part is now ‘sanitized’. So don't forget to convert every occurrence of NOTE: Some PHP servers are configured to solve this issue and they automatically do this conversion.But, why take risk? make it a habit to use htmlentities() with PHP_SELF. See Also
What is PHP_SELF used for?The $_SERVER["PHP_SELF"] is a super global variable that returns the filename of the currently executing script. So, the $_SERVER["PHP_SELF"] sends the submitted form data to the page itself, instead of jumping to a different page. This way, the user will get error messages on the same page as the form.
What is $_ SERVER [' PHP_SELF ']?$_SERVER['PHP_SELF'] Contains the file name of the currently running script. $_SERVER['GATEWAY_INTERFACE'] Contains the version of the Common Gateway Interface being used by the server.
Do I need Htmlspecialchars?You use htmlspecialchars EVERY time you output content within HTML, so it is interpreted as content and not HTML. If you allow content to be treated as HTML, you have just opened the door to bugs at a minimum, and total XSS hacks at worst.
What is Htmlspecialchars?htmlspecialchars() Function: The htmlspecialchars() function is an inbuilt function in PHP which is used to convert all predefined characters to HTML entities. Syntax: string htmlspecialchars( $string, $flags, $encoding, $double_encode ) Parameter value: $string: This parameter is used to hold the input string.
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