Php tables: how to print only array values ​​but not keys


This code loops through a mysql table and prints out empty/null fields. It however prints the array values and the keys like this

Array (
    [0] => Field "dob" on entry "1" is empty/null
    [1] => Field "user_name" on entry "7" is empty/null

How do I print something like this field "dob" on entry "1" is empty/null

$sql = "SELECT * FROM userinfo";
$res = mysql_query($sql);
while ($row = mysql_fetch_array($res)) {
    foreach($row as $key => $field) {
        if(empty($field)) {
            $emptyFields[] = sprintf('Field "%s" on entry "%d" is empty/null', $key,   $row['userid']);

echo implode('<br>', $emptyFields);