How does the "referer" method work in PHP to control access to specific pages, and what are its limitations?

To control access to specific pages based on the referring page, we can use the "referer" method in PHP. This method involves checking the HTTP referer header to determine where the request is coming from. By comparing the referer URL with a predefined list of allowed URLs, we can restrict access to specific pages. However, it's worth noting that the referer header can be easily manipulated or blocked by the user's browser, so it should not be relied upon as the sole method of access control.

if(isset($_SERVER['HTTP_REFERER'])) {
    $allowed_referers = array('http://example.com/page1.php', 'http://example.com/page2.php');
    if(!in_array($_SERVER['HTTP_REFERER'], $allowed_referers)) {
        // Redirect or display an error message
        header('Location: error.php');
        exit();
    }
} else {
    // Handle cases where the referer header is not set
    header('Location: error.php');
    exit();
}