Refuses to get data - php

Question

I am using this code to get the value of checked box in PHP but it doesn't work in the second code. The first one is just a list for testing. The second one will echo data from a database:
When applying the first code on the test list I will get the value of the box I checked but when applying it on the second part (one that gets data from database it returns Empty)
Get the checked boxes:
<?php
if(isset($_POST['DeleteCon']) )
{
if(!empty($_POST['lang']))
{
foreach($_POST['lang'] as $value)
{
echo "value : ".$value.'<br/>';
}
}
else
{
echo "value : Empty <br/>";
}
}
?>
Test list: it works on this section of the code:
<form method="post">
<?php
echo "<span>Select languages</span><br/>
<input type='checkbox' name='lang[]' value='PHP' class='table-row'> PHP <br/>
<input type='checkbox' name='lang[]' value='JavaScript'> JavaScript <br/>
<input type='checkbox' name='lang[]' value='jQuery'> jQuery <br/>
<input type='checkbox' name='lang[]' value='Angular JS'> Angular JS <br/>"
?>
</form>
But doesn't work on this one:
<form method="post">
<?php
include('database.php');
$sql = "SELECT id, ContactID ,FirstName, LastName, Phone FROM Contact WHERE ID='1'";
$result = $conn->query($sql);
if ( !empty($result->num_rows) && $result->num_rows > 0) { // ...
// output data of each row
echo "<form method='post'>";
while($row = $result->fetch_assoc()) {
echo "<tr>
<td id='delete'>
<input type='checkbox' name='lang[]' value='PHP' class='table-row'>
</td>
<td>". $row["FirstName"]. "</td>
<td>". $row["LastName"]. "</td>
<td>". $row["Phone"] ."</td></tr>";
}
echo "</form>";
} else {
echo "<tr>
<td id='delete'>
<input type='checkbox' id='row1' class='table-row'>
</td>
<td> 0 results </tr>";
}
$conn->close();
?>
</form>