Kun ledige klokkeslet

<?php

    /* Reserverede tider findes */
    $dag = date("Y-m-d");
    $sql = "SELECT reservationsId, tidsId FROM tider WHERE dato = '".$dag."' ORDER BY tidsId ASC";
    $query = mysql_query($sql);
    $reserverede_tider = array();
    while( $obj = mysql_fetch(object) )
        $reserverede_tider[] = $obj->tidsId;    

    /* Find ledige tider */

    $dag_start = mktime(8, 0, 0);
    $dag_slut = mktime(16, 0, 0);    
    $klippetid = 60*35; // 60 sekunder gange 35 minutter

    $ledige_tider = array();
    for( $i = $dag_start; $i <= $dag_slut; $i = $i + $klippetid)
    {
        if( !in_array(date("Hi", $i), $reserverede_tider) )
            $ledige_tider[date("Hi", $i)] = date("H:i", $i);
    }
?>

    <select name="tidsId">
    <?php foreach($ledige_tider as $tidsId => $tid): ?>
        <option value="<?php echo (int)$tidsId; ?>"><?php echo $tid; ?></option>
    <?php endforeach; ?>
    </select>

<?php

    /* Reserverede tider findes for den enkelte frisør */
    $frisorId = 1;
    $dag = date("Y-m-d");
    $sql = "SELECT reservationsId, tidsId FROM tider WHERE dato = '".$dag."' AND frisorId = ".$frisorId." ORDER BY tidsId ASC";
    $query = mysql_query($sql);
    $reserverede_tider = array();
    while( $obj = mysql_fetch(object) )
        $reserverede_tider[] = $obj->tidsId;    

    /* Find ledige tider */

    $dag_start = mktime(8, 0, 0);
    $dag_slut = mktime(16, 0, 0);    
    $klippetid = 60*35; // 60 sekunder gange 35 minutter

    $ledige_tider = array();
    for( $i = $dag_start; $i <= $dag_slut; $i = $i + $klippetid)
    {
        if( !in_array(date("Hi", $i), $reserverede_tider) )
            $ledige_tider[date("Hi", $i)] = date("H:i", $i);
    }
?>

    <select name="tidsId">
    <?php foreach($ledige_tider as $tidsId => $tid): ?>
        <option value="<?php echo (int)$tidsId; ?>"><?php echo $tid; ?></option>
    <?php endforeach; ?>
    </select>