WordPress at a glance
function is not described

_wp_cron() WP 5.7.0

Run scheduled callbacks or spawn cron for all scheduled events.

Warning: This function may return Boolean FALSE, but may also return a non-Boolean value which evaluates to FALSE. For information about casting to booleans see the PHP documentation. Use the === operator for testing the return value of this function.

This is an internal function for using it by WP core itself. It's not recommended to use this function in your code.

No Hooks.

Return

Int|false. On success an integer indicating number of events spawned (0 indicates no events needed to be spawned), false if spawning fails for one or more events.

Usage

_wp_cron();

Changelog

Since 5.7.0 Introduced.

Code of _wp_cron() WP 5.7.1

<?php
function _wp_cron() {
	// Prevent infinite loops caused by lack of wp-cron.php.
	if ( strpos( $_SERVER['REQUEST_URI'], '/wp-cron.php' ) !== false || ( defined( 'DISABLE_WP_CRON' ) && DISABLE_WP_CRON ) ) {
		return 0;
	}

	$crons = wp_get_ready_cron_jobs();
	if ( empty( $crons ) ) {
		return 0;
	}

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

	$schedules = wp_get_schedules();
	$results   = array();
	foreach ( $crons as $timestamp => $cronhooks ) {
		if ( $timestamp > $gmt_time ) {
			break;
		}
		foreach ( (array) $cronhooks as $hook => $args ) {
			if ( isset( $schedules[ $hook ]['callback'] ) && ! call_user_func( $schedules[ $hook ]['callback'] ) ) {
				continue;
			}
			$results[] = spawn_cron( $gmt_time );
			break 2;
		}
	}

	if ( in_array( false, $results, true ) ) {
		return false;
	}
	return count( $results );
}