Headers¶
In PHP, headers are HTTP response headers sent to the client before any body output. PHP provides several built-in functions to manage them.
header() sends a raw HTTP header. headers_sent() checks whether headers have already been sent. headers_list() returns the list of headers ready to be sent. header_remove() removes a previously set header.
Headers must be sent before any output (HTML, whitespace, or echo). Sending output before calling header() triggers a PHP warning.
<?php
header('Content-Type: application/json');
header('X-Custom-Header: value');
if (headers_sent($file, $line)) {
echo "Headers already sent in $file on line $line";
}
echo json_encode(['status' => 'ok']);
?>
Related : HTTP Headers, Hyper Text Transfer Protocol (HTTP), Cookie, HTTP Request Headers, Output Buffering
