WordPress filter hook for logging WP HTTP requests

wp_log_http_requests.php

<?php

function wp_log_http_requests( $response, $args, $url ) {

	// set your log file location here
	$logfile = plugin_dir_path( __FILE__ ) . '/http_requests.log';

	// parse request and response body to a hash for human readable log output
	$log_response = $response;
	if ( isset( $args['body'] ) ) {
		parse_str( $args['body'], $args['body_parsed'] );
	}
	if ( isset( $log_response['body'] ) ) {
		parse_str( $log_response['body'], $log_response['body_parsed'] );
	}
	// write into logfile
	file_put_contents( $logfile, sprintf( "### %s, URL: %s\nREQUEST: %sRESPONSE: %s\n", date( 'c' ), $url, print_r( $args, true ), print_r( $log_response, true ) ), FILE_APPEND );

	return $response;
}

// hook into WP_Http::_dispatch_request()
add_filter( 'http_response', 'wp_log_http_requests', 10, 3 );

?>