http_headers_useragent filter-hook . WP 1.0

This filter is documented in wp-includes/class-http.php

Usage

add_filter( 'http_headers_useragent', 'filter_function_name_6020', 10, 2 );
function filter_function_name_6020( $string, $pagelinkedfrom ){
	// filter...

	return $string;
}

$string

-

$pagelinkedfrom

-

Where the hook is called

$user_agent = apply_filters( 'http_headers_useragent', 'WordPress/' . get_bloginfo( 'version' ) . '; ' . get_bloginfo( 'url' ), $pagelinkedfrom );

'user-agent'          => apply_filters( 'http_headers_useragent', 'WordPress/' . get_bloginfo( 'version' ) . '; ' . get_bloginfo( 'url' ), $url ),

Where in WP core the hook is used WordPress