Update is not working in database - php

Question

Dont mind the security issues, this is just local testing, but when ever i click the update button none of the changes go through on the page or on the query and i get no erros.
<?php
$link = mysqli_connect("localhost", "root", "", "test") or die("could not connect");
if (isset($_POST['update'])) {
$updateQuery = (" UPDATE `test1` SET f_name = '$_POST[f_name]', l_name='$_POST[l_name]', email='$_POST[email]' WHERE id='$_POST[id]'");
mysqli_query($link, $updateQuery);
};
$query = ("SELECT * FROM `test1`");
$result = mysqli_query($link, $query);
echo "<table border=1
<tr>
<th>Firstname</th>
<th>Lastname</th>
<th>Email</th>
</tr>";
while($row = mysqli_fetch_array($result)) {
echo "<form method=post action=update.php>";
echo "<tr>";
echo "<td>" . "<input type=text name=f_name value=" . $row['f_name'] . " </td>";
echo "<td>" . "<input type=text name=l_name value=" . $row['l_name'] . " </td>";
echo "<td>" . "<input type=text name=email value=" . $row['email'] . " </td>";
echo "<td>" . "<input type=hidden name=id value=" . $row['id'] . " </td>";
echo "<td>" . "<input type=submit name=submit value=update" . " </td>";
echo "</tr>";
}
?>

Answer 1

change your form to
while($row = mysqli_fetch_array($result)) {
echo "<form method=post action=update.php>";
echo "<input type=hidden name=update>";
echo "<tr>";
echo "<td>" . "<input type=text name=f_name value=" . $row['f_name'] . " </td>";
echo "<td>" . "<input type=text name=l_name value=" . $row['l_name'] . " </td>";
echo "<td>" . "<input type=text name=email value=" . $row['email'] . " </td>";
echo "<td>" . "<input type=hidden name=id value=" . $row['id'] . " </td>";
echo "<td>" . "<input type=submit name=submit value=update" . " </td>";
echo "</tr>";
}

Answer 2

POST keys should be in quotes. Try this instead:
$updateQuery = "UPDATE test1 SET f_name = ".$_POST['f_name'].", l_name=."$_POST['l_name'].", email=".$_POST['email']." WHERE id=".$_POST['id'];

Answer 3

Try this:
$updateQuery = ("UPDATE `test1` SET f_name = '{$_POST['f_name']}', l_name='{$_POST['l_name']}', email='{$_POST['email']}' WHERE id='{$_POST['id']}'");
Also you can try echoing something inside your if (isset($_POST['update'])) { to make sure it is testing true.
Here is your problem:
if (isset($_POST['submit']) && $_POST['submit'] == 'update') {
The name of the submit button is submit not update, the value is update.