<?php
$heure_debut = "10:00";
$heure_fin = "14:00";
$d = new DateTime($heure_debut);
while ($d->format('H:i') <= $heure_fin) {
    echo $d->format('H\hi') . "<br />";
    $d->modify("+20min");
}
?>

<?php
function horaire($heure_debut="00:00", $heure_fin="00:00", $pas=60){
	$horaire = array();
	$d = new DateTime($heure_debut);
	while ($d->format('H:i') <= $heure_fin) {
    	$horaire[] = $d->format('H\hi');
    	$d->modify("+{$pas}min");
	}
	return $horaire;
}
//Appel
$h = horaire("10:00", "14:00", "20");
foreach($h as $valeur) echo $valeur . "<br />";
?>

function horaires($hd,$hf,$gap){
    $hhd=substr($hd,0,2);$mmd=substr($hd,2);
    $hhf=substr($hf,0,2);$mmf=substr($hf,2);
    $deb=mktime($hhd,$mmd);
    $fin=mktime($hhf,$mmf);
    while($deb <= $fin){
        echo date('H:i',$deb).'<br />';
        $deb=strtotime("+$gap minutes",$deb);
        }
    }
horaires('0830','1130',30);

printf("%02d",$val);

$d = new DateTime();
while ($d->format('H') != $heure_fin) {
    $d->modify("+20min");
    echo $d->format('H\hi');
}

$heure_depart=10;
$heure_fin=14; 
for ($i=$hheure_depart;$i<=$heure_fin;$i++) {
for ($j=0;$j<=40;$j+=20) {
echo $i.":".$j;
echo "<BR>";
}
} 

$heure_depart=10;
$heure_fin=14;
for ($i=$heure_depart;i<=$heure_fin;$i++) {
	for ($j=0;$j=<40;$j+=20) {
		echo $i.":".$j;
	}
}