input type hidden does'nt post - php

Question

I have a system where people can indicate whether they are attending an event. There are several events to choose from. The events come from the database and have a unique id. Everything works fine, except the event and date can't be posted together. Only when I make a checkbox of the date (or the event) everything neatly posted. A hidden textfield always posts the wrong date or event.
<form action="insert.php" method="post">
<?php
/* Attempt MySQL server connection. Assuming you are running MySQL
server with default setting (user 'root' with no password) */
$link = mysqli_connect("localhost", "user", "pass", "db");
// Check connection
if($link === false){
die("ERROR: Could not connect. " . mysqli_connect_error());
}
$sql = "SELECT * FROM events WHERE datum >= CURDATE() AND toon > 0 ORDER BY datum";
if($result = mysqli_query($link, $sql)){
if(mysqli_num_rows($result) > 0){
while($row = mysqli_fetch_array($result)){
echo "<input type=\"radio\" id=\"datum\" name=\"datum\" value=\" "; echo "" . $row['datum'] . "\" required> ";
echo "<input type=\"checkbox\" id=\"event\" name=\"event\" value=\" "; echo "" . $row['event'] . "\"> ";
print date('l d/m/Y', strtotime($row['datum']));
echo " • ";
if(strlen($row['url']) > 0):
echo " <a href=\" " . $row['url'] . " \" target=\"_blank\">";
endif;
echo "" . $row['event'] . "</a>";
echo " • " . $row['info'] . "";
echo "<br>";
}
// Free result set
mysqli_free_result($result);
} else{
echo "No records matching your query were found.";
}
} else{
echo "ERROR: Could not able to execute $sql. " . mysqli_error($link);
}
// Close connection
mysqli_close($link);
?>
<br><br>
<label for="naam">Naam:</label>
<input type="text" name="naam" id="naam" placeholder="Jouw naam..." required>
<input type="hidden" id="mee" name="mee" value="mee">
<label for="opmerking">Opmerking:</label>
<input type="text" name="opmerking" id="opmerking" placeholder="Eventuele opmerkingen...">
<input type="hidden" id="toon" name="toon" value="0">
<input type="submit" value="Ik ga mee!" class="w3-button w3-black">
</form>
</div>

Answer 1

There are a number of issues
Each input must have a different name, otherwise how are you going to know which one has been entered?
Because you have used escape characters for the double quotes, there is confusion there. To, clarify I have used single quotes inside.
Each id must also be unique
As a suggestion, in the loop
$event = $row['event'];
echo "<input type='radio' id='datum-$event' name='datum-$event' value='' $row['datum'] required> ";
So, now the id and name are unique. When this radio button is selected you will have
$_POST['datum-eventname'];
You dont need two inputs in the loop.