<?php
$str="1|苹果|30
1|桃子|50
1|普通|10
2|小麦|100
2|玉米|35
2|大米|30
3|电脑|5
3|MP3|121
3|打印机|8";
$strArray=explode("\n",$str);
/*关键的是下面的代码*/
$result=array();
foreach($strArray as $item)
{
  $itemArray=explode('|',$item);
  $result[$itemArray[0]][]=$item;
}
echo "<pre>";
print_r($result);
echo "<pre>";
?>

<pre>Array
(
  [1] => Array
    (
      [0] => 1|苹果|30
      [1] => 1|桃子|50
      [2] => 1|普通|10
    )
  [2] => Array
    (
      [0] => 2|小麦|100
      [1] => 2|玉米|35
      [2] => 2|大米|30
    )
  [3] => Array
    (
      [0] => 3|电脑|5
      [1] => 3|MP3|121
      [2] => 3|打印机|8
    )
)
<pre>