Determining the referer in PHP
$_SERVER['HTTP_REFERER']Provides us with a referrer URLto determine the user request on the server. However, this is not a best practice because the referrer can be HTTPcompromised through .
$_SESSION[]Determine the referrer
in PHP using
Since HTTP_REFERERcan be spoofed/forged, PHP allows us to use sessions/cookies to determine if an incoming user request is coming from your domain (server).
We will create two demonstration pages for this article.
userrequest.phpCode:
<!DOCTYPE html>
<body>
<form action ="determineuser.php" method ="post" align="center">
<input type ="submit" name="click" value="Determine user request through session"/>
<?php
session_start(); //first we start session
$setsession = uniqid(mt_rand(), TRUE); //Set it true, assign mt_rand to ensure secuity
$_SESSION['set'] = $setsession;
//we can use url to export session over servers
$redirect = "determineuser.php?set={$setsession}"; // this url can be on any server
?>
<br>
<h1 align="center">
<?php
echo "Your current session is:".$_SESSION['set']; //check session on page 1
echo"<br>";
?>
</form>
</body>
</html>
determineuser.phpCode:
<?php
session_start(); //check if the session and form input is set
if ( (isset( $_SESSION[ 'set' ] ) && $_SESSION[ 'set' ] === TRUE ) || isset( $_POST[ 'click' ] ) ) {
echo "Determined Last visited page on the server using HTTP REFERER:<br>".$_SERVER['HTTP_REFERER'];
?>
<h1 align="center">
<p> This is the secure way to determine referer using session:</p>
<?php
echo $_SESSION['set'];//check session on page 2 (compare to determine from the last page)
?>
</h1>
<?php
} else {
//if the domain referer is not determined, header function will redirect the user page to the last page
header('Location:userrequest.php');
exit; //exit to release unnessary server load
}
?>
</form>
</body>
</html>
Output:
It is important to note that refererthe traditional method of determining is not reliable in most cases, but is still widely used. To be safer, we recommend using sessionor ( AJAX) instead of HTTP.
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