while-loop not working properly - php

Question

I want to create a page, where I can create Keys, and save them in a databank, but I got some problems.
There is a textfield, where you can write in, how many keys you want to create. For example I write 5 in, but it does only 3 entrys in the databank, but down in the code is an echo command, which says that he did it 5 times, here is a screenshot:
Also, what I noticed is, that the website is doing max 3 entrys in the databank, for example I write 10, and he still only does 3 entrys.
If I write only 1-3 keys, the while-loop is working.
echo "<p><a href='key.php'>Betakey administration</a></p>";
echo "<form action='#' method='POST'>";
echo "<input type='number' name='numberkeys' placeholder='Number of Keys'>";
echo "<br>";
echo "<input type='submit' name='createkey' value='Create Key'>";
echo "<input type='submit' name='keyanzeigen' value='Show all Keys'>";
echo "<input type='submit' name='unusedkeys' value='Show all unused Keys'>";
echo "<input type='submit' name='usedkeys' value='Show all used Keys'>";
echo "</form>";
$createdkeys=0;
if(isset($_POST['createkey'])){
$minus= array(5,10,15);
while($createdkeys<$_POST['numberkeys']){
//creation of the keys
for($i=1;$i<20 ;$i++){
if(in_array($i,$minus)){
$key=$key."-";
}
else{
$key=$key.mt_rand(0,9);
}
//the key looks like this: 1234-5678-1234-5678
}
//here it checks, if the key already exists
$check = mysqli_query($db,"SELECT keyy FROM keyys WHERE keyy='$key'");
$check = mysqli_fetch_array($check);
//if the code not exists, the website will insert the key in the databank
//the website will echo the variable $createdkeys and increase the variable $createdkeys by one
if(!isset($check)){
$createdkeys= $createdkeys+1;
echo "<p>".$createdkeys."</p>";
mysqli_query($db,"INSERT INTO keyys VALUES('$key','NO')");
}
}
}