Self submit a form values using PHP_SELF

In some cases, we want to submit some form data in web pages to itself. We can achieve this by using PHP_SELF variable in action field of the form.

This PHP_SELF variable returns the name and path of the current file. So when we use PHP_SELF variable in action field of the form, form values are submitted to same page.

Through this post, we are making a simple page to understand the use of the PHP_SELF variable. This page has some basic form field & when user submit the form values, it will produce a welcome message for the user.

In our page, we have HTML & PHP code. So we name our file as welcome.php. Now first we can create form handler script in our page that will welcome our user.

<?php
	if(isset($_POST['submit']))
	{

		echo "Welcome ". $_POST["name"]."<br>";
		echo "Your email address is: ". $_POST["email"]."</br>";
	}
?>

In our form handler script, we add an if statement to check the status of submit button. Using this if statement, our PHP script only display a welcome message after the user submit the form value.

Now we can add our HTML form in this same page.

<form method="post" action="<?php echo $_SERVER['PHP_SELF']; ?>">
	Name: <input type="text" name="name"><br>
	E-mail: <input type="text" name="email"><br>
	<input type="submit" value="submit">
</form>

Have you noticed the action in our HTML form? It utilize the PHP_SELF variable & thus the form values are submitted to same page. So after the form submission, the form data are available on the same page.

But when we use PHP_SELF variable in our form’s action, it will open a door for hackers. We want to understand & avoid this exploit. You can read about a normal practice to escape from this vulnerability from here.

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This article was published on December 17, 2013

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