How Can I Access Any HTTP Request Header in PHP?

How to Read Any Request Header in PHP

Problem:

How can you access any HTTP header, including custom headers, in PHP?

Answer:

There are several methods to read request headers in PHP, depending on your specific requirements:

Single Header Retrieval:

If you only need to retrieve a single header value, use the following syntax:

<?php
// Replace XXXXXX_XXXX with the name of the header you need in UPPERCASE (and with '-' replaced by '_')
$headerStringValue = $_SERVER['HTTP_XXXXXX_XXXX'];
?>

Apache Module or FastCGI (PHP 5.4 ):

If PHP is running as an Apache module or using FastCGI with PHP 5.4 or later, you can use the apache_request_headers() function:

<?php
$headers = apache_request_headers();

foreach ($headers as $header => $value) {
    echo "$header: $value <br />\n";
}
?>

Fallback Method:

In all other cases, you can use the following userland implementation:

<?php
function getRequestHeaders() {
    $headers = array();
    foreach($_SERVER as $key => $value) {
        if (substr($key, 0, 5) != 'HTTP_') {
            continue;
        }
        $header = str_replace(' ', '-', ucwords(str_replace('_', ' ', strtolower(substr($key, 5)))));
        $headers[$header] = $value;
    }
    return $headers;
}

$headers = getRequestHeaders();

foreach ($headers as $header => $value) {
    echo "$header: $value <br />\n";
}
?>

Additional Functions:

• getallheaders() (PHP 5.4 ): Alias of apache_request_headers().
• apache_response_headers(): Fetches all HTTP response headers.
• headers_list(): Fetches a list of headers to be sent.

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