headers_list() will return a list of headers to be sent
to the browser / client. To determine whether or not these headers have
been sent yet, use headers_sent().
Parameters
This function has no parameters.
Return Values
Returns a numerically indexed array of headers.
Examples
Example #1 Example using headers_list()
<?php
/* setcookie() will add a response header on its own */
setcookie('foo', 'bar');
/* Define a custom response header
This will be ignored by most clients */
header("Example-Test: foo");
/* Specify plain text content in our response */
header('Content-Type: text/plain; charset=UTF-8');
/* What headers are going to be sent? */
var_dump(headers_list());
?>
The above example will output
something similar to: