Finde fortløbne numre i MySQL og få dem ud i PHP.

<?php
function get_ids_from_database() {
    $res = array();
    $con = mysqli_connect('localhost', 'root', '', 'Test') or die(mysqli_connect_error());
    $stmt = mysqli_prepare($con, 'SELECT id FROM tbl') or die(mysqli_error($con));
    mysqli_stmt_execute($stmt) or die(mysqli_error($con));
    $rs = mysqli_stmt_get_result($stmt);
    while($row = mysqli_fetch_array($rs, MYSQLI_ASSOC)) {
        $res[] = $row['f1'];
    }
    mysqli_stmt_close($stmt);
    mysqli_close($con);
    return $res;
}

$inuse = get_ids_from_database();
$all = range($inuse[0], $inuse[count($inuse)-1]);
$diff = array_diff($all, $inuse);

foreach($diff as $id) {
    echo $id . "\r\n";
}
?>