PHP二维数组根据某一字段去重或统计

$arr = array(
			array('province'=>'甘肃','name'=>'甲'),
			array('province'=>'天津','name'=>'乙'),
			array('province'=>'天津','name'=>'丙')
		);
		$result = array();
		foreach ($arr as $key=>$value){
			$result[$value['province']] += 1;
		}
		dump($result);

$result = array(
			'甘肃'=>1,
			'天津'=>2
		);

$arr = array(  
            array('province'=>'甘肃','number'=>100),  
            array('province'=>'天津','number'=>200),  
            array('province'=>'天津','number'=>300)  
); 
需要得到如下结果：

$arr = array(  
            array('province'=>'甘肃','number'=>100),  
            array('province'=>'天津','number'=>500)
);

$result = array();
		foreach ($arr as $key=>$value){
			$result[$value['province']] += $value['number'];
		}
		dump($result);