数组用下标来重组数组，为什么重组出来的数组下标一直是第一个?

<?php$id = array(8,31,32);$resarr = array();foreach($id as $num){	$product = array(					array(						'pid'=>'10', 						'name'=>'产品1'						),					array(						'pid'=>'11', 						'name'=>'产品2'						)					);	foreach($product as $key => $value)	{		$result_value = "";		foreach($value as $k => $v)		{			$result_value .= $result_value ? "|" : "";			$result_value .=  $v['pid'];		}		$product[$key]['value'] = $result_value;	}	$resarr[$num] = $product;	var_dump($resarr);	echo "<hr />";}

$id = array(8,31,32);$resarr = array();foreach($id as $num){	$product = array(					array(						'pid'=>'10', 						'name'=>'产品1'						),					array(						'pid'=>'11', 						'name'=>'产品2'						)					);	foreach($product as $key => $value)	{		$result_value = "";		foreach($value as $k => $v)		{			$result_value .= $result_value ? "|" : "";			$result_value .=  $v['pid'];		}		$product[$key]['value'] = $result_value;	}	$resarr[$num] = $product;	}var_dump($resarr);echo "<hr />";