spawn_cron( int $gmt_time )

function spawn_cron( $gmt_time = 0 ) {
	if ( ! $gmt_time )
		$gmt_time = microtime( true );

	if ( defined('DOING_CRON') || isset($_GET['doing_wp_cron']) )
		return;

	/*
	 * Get the cron lock, which is a Unix timestamp of when the last cron was spawned
	 * and has not finished running.
	 *
	 * Multiple processes on multiple web servers can run this code concurrently,
	 * this lock attempts to make spawning as atomic as possible.
	 */
	$lock = get_transient('doing_cron');

	if ( $lock > $gmt_time + 10 * MINUTE_IN_SECONDS )
		$lock = 0;

	// don't run if another process is currently running it or more than once every 60 sec.
	if ( $lock + WP_CRON_LOCK_TIMEOUT > $gmt_time )
		return;

	//sanity check
	$crons = _get_cron_array();
	if ( !is_array($crons) )
		return;

	$keys = array_keys( $crons );
	if ( isset($keys[0]) && $keys[0] > $gmt_time )
		return;

	if ( defined( 'ALTERNATE_WP_CRON' ) && ALTERNATE_WP_CRON ) {
		if ( 'GET' !== $_SERVER['REQUEST_METHOD'] || defined( 'DOING_AJAX' ) ||  defined( 'XMLRPC_REQUEST' ) ) {
			return;
		}

		$doing_wp_cron = sprintf( '%.22F', $gmt_time );
		set_transient( 'doing_cron', $doing_wp_cron );

		ob_start();
		wp_redirect( add_query_arg( 'doing_wp_cron', $doing_wp_cron, wp_unslash( $_SERVER['REQUEST_URI'] ) ) );
		echo ' ';

		// flush any buffers and send the headers
		while ( @ob_end_flush() );
		flush();

		WP_DEBUG ? include_once( ABSPATH . 'wp-cron.php' ) : @include_once( ABSPATH . 'wp-cron.php' );
		return;
	}

	// Set the cron lock with the current unix timestamp, when the cron is being spawned.
	$doing_wp_cron = sprintf( '%.22F', $gmt_time );
	set_transient( 'doing_cron', $doing_wp_cron );

	/**
	 * Filters the cron request arguments.
	 *
	 * @since WP-3.5.0
	 * @since WP-4.5.0 The `$doing_wp_cron` parameter was added.
	 *
	 * @param array $cron_request_array {
	 *     An array of cron request URL arguments.
	 *
	 *     @type string $url  The cron request URL.
	 *     @type int    $key  The 22 digit GMT microtime.
	 *     @type array  $args {
	 *         An array of cron request arguments.
	 *
	 *         @type int  $timeout   The request timeout in seconds. Default .01 seconds.
	 *         @type bool $blocking  Whether to set blocking for the request. Default false.
	 *         @type bool $sslverify Whether SSL should be verified for the request. Default false.
	 *     }
	 * }
	 * @param string $doing_wp_cron The unix timestamp of the cron lock.
	 */
	$cron_request = apply_filters( 'cron_request', array(
		'url'  => add_query_arg( 'doing_wp_cron', $doing_wp_cron, site_url( 'wp-cron.php' ) ),
		'key'  => $doing_wp_cron,
		'args' => array(
			'timeout'   => 0.01,
			'blocking'  => false,
			/** This filter is documented in wp-includes/class-wp-http-streams.php */
			'sslverify' => apply_filters( 'https_local_ssl_verify', false )
		)
	), $doing_wp_cron );

	wp_remote_post( $cron_request['url'], $cron_request['args'] );
}