What best practices should be followed when implementing access control based on referrers in PHP?

When implementing access control based on referrers in PHP, it is important to validate the referrer header to ensure that requests are coming from trusted sources. This can help prevent unauthorized access to sensitive resources on your website. One best practice is to compare the referrer header with a list of allowed referrers and only grant access if there is a match. 

$allowed_referrers = array("https://www.example.com", "https://subdomain.example.com");

$referrer = $_SERVER['HTTP_REFERER'];

if(in_array($referrer, $allowed_referrers)) {
    // Access granted
    echo "Access granted";
} else {
    // Access denied
    echo "Access denied";
}

Keywords

access control referrers PHP security implementation

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