wp-includes/class-wp-http.php:541Tests which transports are capable of supporting the request.
$argsarray$urlstringoptionalnullstring|falseOne hook fires while WP_Http::_get_first_available_transport() runs, in this order:
Filters which HTTP transports are available and in what order.
public function _get_first_available_transport( $args, $url = null ) { $transports = array( 'curl', 'streams' ); /** * Filters which HTTP transports are available and in what order. * * @since 3.7.0 * @deprecated 6.4.0 Use WpOrg\Requests\Requests::get_transport_class() * * @param string[] $transports Array of HTTP transports to check. Default array contains * 'curl' and 'streams', in that order. * @param array $args HTTP request arguments. * @param string $url The URL to request. */ $request_order = apply_filters_deprecated( 'http_api_transports', array( $transports, $args, $url ), '6.4.0' ); // Loop over each transport on each HTTP request looking for one which will serve this request's needs. foreach ( $request_order as $transport ) { if ( in_array( $transport, $transports, true ) ) { $transport = ucfirst( $transport ); } $class = 'WP_Http_' . $transport; // Check to see if this transport is a possibility, calls the transport statically. if ( ! call_user_func( array( $class, 'test' ), $args, $url ) ) { continue; } return $class; } return false; }Introduced in 3.2.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/class-wp-http.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.