PHP Check MySQL Last Row

You can use mysqli_num_rows() prior to your while loop, and then use that value for your condition:

$numResults = mysqli_num_rows($result);
$counter = 0
while ($row = mysqli_fetch_array($result)) {
    if (++$counter == $numResults) {
        // last row
    } else {
        // not last row
    }
}

$result = mysql_query("SELECT *SOMETHING* ");

$i = 1;
$allRows = mysql_num_rows($result);
while($row = mysql_fetch_array($result)){

    if ($allRows == $i) {
        /* Do Something Here*/
    } else {
        /* Do Another Thing Here*/}
    }
    $i++;
}

but please take in consideration PDO

$db = new PDO('mysql:host=localhost;dbname=testdb', 'username', 'password');
$stmt = $db->query("SELECT * FROM table");
$allRows = $stmt->rowCount();
$i = 1;
while($row = $stmt->fetch(PDO::FETCH_ASSOC)) {

    if ($allRows == $i) {
        /* Do Something Here*/
    } else {
        /* Do Another Thing Here*/}
    }
    $i++;
}