array (size=2) 'id' => int 139 'key' => string '11111' array (size=2) 'id' => int 139 'key' => string '22222' array (size=2) 'id' => int 159 'key' => string '33333'array (size=2) 'id' => int 159 'key' => string '44444'

合并为
array (size=2) 'id' => int 139 'key' => string '11111，22222' array (size=2) 'id' => int 159 'key' => string '33333，44444'

回复内容： array (size=2) 'id' => int 139 'key' => string '11111' array (size=2) 'id' => int 139 'key' => string '22222' array (size=2) 'id' => int 159 'key' => string '33333'array (size=2) 'id' => int 159 'key' => string '44444'

合并为
array (size=2) 'id' => int 139 'key' => string '11111，22222' array (size=2) 'id' => int 159 'key' => string '33333，44444'

$arr = [ [id=>139, key=>111], [id=>139, key=>222], [id=>159, key=>333], [id=>159, key=>444]];$res = [];foreach( $arr as $item ) $res[ $item['id'] ][] = $item['key'];