WordPress at a glance
filter is not described

wp_headers filter-hook . WP 2.8.0

Filters the HTTP headers before they're sent to the browser.

Usage

add_filter( 'wp_headers', 'filter_function_name_7483', 10, 2 );
function filter_function_name_7483( $headers, $this ){
	// filter...

	return $headers;
}
$headers(array)
The list of headers to be sent.
$this(WP)
Current WordPress environment instance.

Where the hook is called

WP::send_headers()
wp-includes/class-wp.php 467
$headers = apply_filters( 'wp_headers', $headers, $this );

Where the hook is used (in WP core)

wp-includes/class-wp-customize-manager.php 1841
add_filter( 'wp_headers', array( $this, 'filter_iframe_security_headers' ) );