How Can I Access Request Headers in PHP?

Accessing Request Headers in PHP

Retrieving specific or all request headers is a common task in PHP development. Here are the different approaches you can use:

Single Header Retrieval (Apache Module or FastCGI)

If you only need a particular header, the most efficient way is to access it directly using the HTTP header name as the key in the $_SERVER array. Replace XXXXXX_XXXX with the header name in uppercase (with hyphens replaced by underscores).

// Retrieve the "X-Requested-With" header value
$headerValue = $_SERVER['HTTP_X_REQUESTED_WITH'];

All Headers Retrieval

Apache Module or FastCGI (Simple Method)

The apache_request_headers() function provides access to all request headers.

$headers = apache_request_headers();

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

All Other Cases (Userland Implementation)

In cases where apache_request_headers() is unavailable, you can use a custom function to extract headers from the $_SERVER array.

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 Resources:

• getallheaders() (PHP >= 5.4): An alternative to apache_request_headers() that works cross-platform.
• apache_response_headers(): Retrieves HTTP response headers.
• headers_list(): Lists headers to be sent in the response.

The above is the detailed content of How Can I Access Request Headers in PHP?. For more information, please follow other related articles on the PHP Chinese website!