arrays implode

<!DOCTYPE html>
<html>
<head>
  <title>array</title>
</head>
<body>
<?php
$sql_select = "SELECT * FROM cart";
$run_select = mysqli_query($con,$sql_select);
$datas = array();
if (mysqli_num_rows($run_select) > 0) {

while ($show = mysqli_fetch_assoc($run_select)) {

  $id[] = $show;
 }
}

//print_r($datas);
 /*echo "cid";
foreach ($datas as $id) {
  echo $id['cid'].",";
}

echo "<br/> p_id";
foreach ($datas as $p_id) {
  echo $p_id['p_id'].",";
}
echo "<br/> ip_add";
foreach ($datas as $ip_add) {
  echo $ip_add['ip_add'].",";
}

echo "<br/>  quantity";
foreach ($datas as $qty) {
  echo $qty['qty'].",";
}
*/
$avengers = implode(",", $id['1']);

echo $avengers;
?>