Something like this?
$arr = [
['ahmed', 'omar' , 'ali'],
['mohammed', 'sayed'],
['mostafa', 'ali'],
];
$arr2 = array_map('implode_arr', $arr);
function implode_arr($value) {
return implode(', ', $value);
}
Gives this
Array
(
[0] => ahmed, omar, ali
[1] => mohammed, sayed
[2] => mostafa, ali
)