sequence.php

<?php

/* ... */

	/**
	 * Allows each Mongo collection to have a sequence ID for numbering objects.
	 *
	 * @param array $scope The scope for this counter. A scope is an array of key/value pairs
	 *              that represent the conditions used to group this sequence. For example, a
	 *              scope may be the ID of a company, allowing each company to have their own
	 *              unique sequence.
	 */
	static public function seq(array $scope = []) {
		$seq = static::connection()->connection->command([
			'findandmodify' => 'seq',
			'query' => ['source' => static::meta('source')] + $scope,
			'update' => ['$inc' => ['seq' => 1]],
			'upsert' => true,
			'new' => true
		]);
		return $seq['value']['seq'];
	}

/* ... */

?>