php 数组中相同值的组成新的数组

<?php //原数组 $arr = [ ['product_id'=>33, 'seller_id'=>8], ['product_id'=>32, 'seller_id'=>7], ['product_id'=>31, 'seller_id'=>6], ['product_id'=>33, 'seller_id'=>5], ['product_id'=>33, 'seller_id'=>8], ]; $p = []; $pp = []; if(!empty($arr)){ //结果1 foreach($arr as $v){ isset($p[$v['product_id']]) || $p[$v['product_id']] = []; $p[$v['product_id']][] = $v['seller_id']; $pp[$v['product_id']] .= $v['seller_id'].','; } //结果2 foreach($pp as &$v1){ $v1 = trim($v1, ','); } } //打印输出分别为 //打印1 echo '<pre>'; print_r($p); echo '</pre>'; //输出1 Array ( [33] => Array ( [0] => 8 [1] => 5 [2] => 8 ) [32] => Array ( [0] => 7 ) [31] => Array ( [0] => 6 ) ) //打印2 echo '<pre>'; print_r($pp); echo '</pre>'; //输出2 Array ( [33] => 8,5,8 [32] => 7 [31] => 6 ) ?>