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filter is not described

http_api_transports filter-hook . WP 3.7.0

Filters which HTTP transports are available and in what order.

Usage

add_filter( 'http_api_transports', 'filter_function_name_9373', 10, 3 );
function filter_function_name_9373( $transports, $args, $url ){
	// filter...

	return $transports;
}
$transports(array)
Array of HTTP transports to check.
Default: array contains 'curl', and 'streams', in that order
$args(array)
HTTP request arguments.
$url(string)
The URL to request.

Where the hook is called

WP_Http::_get_first_available_transport()
wp-includes/class-http.php 509
$request_order = apply_filters( 'http_api_transports', $transports, $args, $url );

Where the hook is used (in WP core)

Does not used.