Question

How should I read any header in PHP?

For example the custom header: X-Requested-With.

Answer 1

IF: you only need a single header, instead of all headers, the quickest method is:

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

ELSE IF: you run PHP as an Apache module or, as of PHP 5.4, using FastCGI (simple method):

apache_request_headers()

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

ELSE: In any other case, you can use (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'; } 

See Also:
getallheaders() – (PHP >= 5.4) cross platform edition Alias of apache_request_headers() apache_response_headers() – Fetch all HTTP response headers.
headers_list() – Fetch a list of headers to be sent.