class Sklad 
{
	private $type = '';
	private $fail = false;
	private $half = false;
	
	private $plus = array(
						'up',
						'fail_up',
						'half_up',
					);
	private $minus = array(
						'down',
						'fail_down',
						'half_down',
					);
	private $update = '';
	
	/*
		Запрос остатков на складе. 
		Если передан массив, вытаскиваем только эти позиции
	*/
	public function ostatki($array_in = array())
	{
		$where = '1';
		if (count($array_in) > 0){
			foreach ($array_in AS $value){
				$tovar[] = $value['tovar'];
			}
			$where = "tovar IN (".implode(',',$tovar).") ";
		}
		
		$sql = "
		SELECT 
			tovar, number 
		FROM 
			`sklad_sklad` 
		WHERE	
			$where
		ORDER BY 
			tovar
		";
		$sql = mysql_query($sql);
		while ($ostatki = mysql_fetch_assoc($sql)) {
			$sklad_tovar[$ostatki['tovar']] = $ostatki['number'];
		}
		return $sklad_tovar;
	}
	
	/*
		Добавить/Списать со склада во время добавления 
		$array = array('tovar'=>$value['tovar'],'number'=>$value['number']);
	*/
	public function plus_minus($array, $type) 
	{ 
		$this->type = $type;
		
		if (!is_array($array))
			return false;
		
		$sklad_tovar = $this->ostatki($array);
		$plus_minus = $this->skladType($array);
		
		if (empty($plus_minus))
			return false;
		
		$update_tovar = array();
		$add_array = array();
		foreach ($plus_minus AS $tovar=>$number) {
			if (isset($sklad_tovar[$tovar])) {
				$update_tovar[] = $tovar;
				$update .=  " WHEN `tovar` = $tovar THEN `". $this->update ."` +$number";
			} else {
				if (empty($this->fail) AND empty($this->half))
					$add_array[] = "('".mysql_real_escape_string($tovar)."', '$number', 0, 0)";
				if (!empty($this->fail))
					$add_array[] = "('".mysql_real_escape_string($tovar)."', 0, '$number', 0)";
				if (!empty($this->half))
					$add_array[] = "('".mysql_real_escape_string($tovar)."', 0, 0,'$number')";
			}
		
		}
		
		// Обновляем что есть
		if (count($update_tovar) > 0){
			$sql = "UPDATE `sklad_sklad` SET ". $this->update ." = CASE ";
			$sql .= $update ." END  WHERE tovar IN (".implode(',',$update_tovar).")";
			$result[] = $sql;
			//mysql_query($sql);
		}
		
		// Добавляем новые позиции
		if (count($add_array) > 0){
			$sql = "INSERT INTO `sklad_sklad` (`tovar`, `number`, `fail`, `half`) VALUE ". implode(',',$add_array);
			$result[] = $sql;
			//mysql_query($sql);
		}
		
		return $result;
		//return true;
	}
	
	/*
		$type = up, down, fail_up, fail_down, half_up, half_down
	*/
	private function skladType($array) 
	{
		switch ($this->type) {
			// Количество
			case 'up':
			case 'down':
				$this->update = 'number';
				break;
			// Брак
			case 'fail_up':
			case 'fail_down':
				$this->update = 'fail';
				$this->fail = true;
				break;
			// Заготовка
			case 'half_up':
			case 'half_down':
				$this->update = 'half';
				$this->half = true;
				break;
			default:
				return false;
		}
		
		foreach ($array AS $value){
			if (in_array($this->type, $this->plus)){
				$plus_minus[$value['tovar']] += $value['number'];
			}
			if (in_array($this->type, $this->minus)){
				$plus_minus[$value['tovar']] -= $value['number'];
			}
		}
		return $plus_minus;
	}
	
}

	$type = 'down';
$array_test = array('0650100', '0890000', '0900000', '0910000', '0950000', '0990000', '8000000', '8100000');
$array = array();
foreach ($array_test AS $tovar){
	$add_product[] = array(
		'tovar'=>$tovar, 
		'number'=>rand(1,10), 
	);
}

$sklad = new sklad();
$return = $sklad->plus_minus($add_product, $type);
if (empty($return)){
	echo 'False';
}
if (is_array($return)){
	echo '<pre>';
	print_r($return);
	echo '</pre>';
}

Array
(
    [0] => UPDATE `sklad_sklad` SET number = CASE  WHEN `tovar` = 0650100 THEN `number` +-6 WHEN `tovar` = 0890000 THEN `number` +-4 WHEN `tovar` = 0900000 THEN `number` +-6 WHEN `tovar` = 0910000 THEN `number` +-10 WHEN `tovar` = 0950000 THEN `number` +-4 WHEN `tovar` = 0990000 THEN `number` +-1 END  WHERE tovar IN (0650100,0890000,0900000,0910000,0950000,0990000)
    [1] => INSERT INTO `sklad_sklad` (`tovar`, `number`, `fail`, `half`) VALUE ('8000000', '-5', 0, 0),('8100000', '-3', 0, 0)
)