php数组根据某键值，把相同键值的合并最终生成一个新的二维数组

要处理的PHP数组：

$infos = array(
array(
'gid' => 36,
'name' => '高二佳木斯',
'start_time' => '2015-08-28 00:00:00',
'pic' => '2015/08/438488a00b3219929282e3652061c2e3.png'
),
array(
'gid' => 36,
'name' => '高二佳木斯',
'start_time' => '2015-08-20 00:00:00',
'pic' => '2015/08/438488a00b3219929282e3652061c2e3.png'
),
array(
'gid' => 36,
'name' => '高二佳木斯',
'start_time' => '2015-08-28 00:00:00',
'pic' => '2015/08/438488a00b3219929282e3652061c2e3.png'
),
array(
'gid' => 36,
'name' => '高二佳木斯',
'start_time' => '2015-08-27 00:00:00',
'pic' => '2015/08/438488a00b3219929282e3652061c2e3.png'
),
array(
'gid' => 18,
'name' => '天书',
'start_time' => '2015-08-24 00:00:00',
'pic' => 'dev/2015/08/438488a00b3219929282e3652061c2e3.png'
),
array(
'gid' => 17,
'name' => '晒黑西游',
'start_time' => '2015-08-06 00:00:00',
'pic' => ''
)
array(
'gid' => 17,
'name' => '晒黑西游',
'start_time' => '2015-08-24 00:00:00',
'pic' =>
)
);
处理要求：将数组中gid相同的二维数组合并到一个数组中，生成一个新的二维数组

代码：

$result= array();
foreach ($infos as $key => $info) {
$result[$info['gid']][] = $info;
}
print_r($result);
output:

Array(
[36] => Array(
[0] => Array(
[gid] => 36
[name] => 高二佳木斯
[start_time] => 2015-08-28 00:00:00
[pic] => dev/2015/08/438488a00b3219929282e3652061c2e3.png
)
[1] => Array(
[gid] => 36
[name] => 高二佳木斯
[start_time] => 2015-08-20 00:00:00
[pic] => dev/2015/08/438488a00b3219929282e3652061c2e3.png
)
[2] => Arra(
[gid] => 36
[name] => 高二佳木斯
[start_time] => 2015-08-28 00:00:00
[pic] => dev/2015/08/438488a00b3219929282e3652061c2e3.png
)
[3] => Array(
[gid] => 36
[name] => 高二佳木斯
[start_time] => 2015-08-27 00:00:00
[pic] => dev/2015/08/438488a00b3219929282e3652061c2e3.png
)
)
[18] => Array(
[0] => Array(
[gid] => 18
[name] => 天书
[start_time] => 2015-08-24 00:00:00
[pic] => dev/2015/08/438488a00b3219929282e3652061c2e3.png
)
)
[17] => Array(
[0] => Arra(
[gid] => 17
[name] => 晒黑西游
[start_time] => 2015-08-06 00:00:00
[pic] =>
)
[1] => Array(
[gid] => 17
[name] => 晒黑西游
[start_time] => 2015-08-24 00:00:00
[pic] =>
)
)
);