<input type="checkbox" name="meyve[]" value="elma" />
<input type="checkbox" name="meyve[]" value="armut" />
<input type="checkbox" name="meyve[]" value="muz" />

$temp = "";
foreach($_POST['meyve'] as $meyve) {
    $temp .= $meyve . "+";
}
$temp = rtrim($temp, "+");
printf("siteadresi.com/istenenler-%s/", $temp);