my code
<select name="select_du">
<option value="0:05" <?if ($flight_duration=='0:05') echo "selected";?>>0:05</option>
<option value="0:10"<?if ($flight_duration=='0:10') echo "selected";?>>0:10</option>
<option value="0:15"<?if ($flight_duration=='0:15') echo "selected";?>>0:15</option>
<option value="0:20"<?if ($flight_duration=='0:20') echo "selected";?>>0:20</option>
<option value="0:25"<?if ($flight_duration=='0:25') echo "selected";?>>0:25</option>
<option value="0:30"<?if ($flight_duration=='0:30') echo "selected";?>>0:30</option>
<option value="0:35"<?if ($flight_duration=='0:35') echo "selected";?>>0:35</option>
<option value="0:40"<?if ($flight_duration=='0:40') echo "selected";?>>0:40</option>
<option value="0:45"<?if ($flight_duration=='0:45') echo "selected";?>>0:45</option>
<option value="0:50"<?if ($flight_duration=='0:50') echo "selected";?>>0:50</option>
<option value="0:55"<?if ($flight_duration=='0:55') echo "selected";?>>0:55</option>
<option value="0:60"<?if ($flight_duration=='0:60') echo "selected";?>>0:60</option>
<option value="0:65"<?if ($flight_duration=='0:65') echo "selected";?>>0:65</option>
<option value="0:70"<?if ($flight_duration=='0:70') echo "selected";?>>0:70</option>
<option value="0:75"<?if ($flight_duration=='0:75') echo "selected";?>>0:75</option>
<option value="0:80"<?if ($flight_duration=='0:80') echo "selected";?>>0:80</option>
<option value="0:85"<?if ($flight_duration=='0:85') echo "selected";?>>0:85</option>
<option value="0:90" <?if ($flight_duration=='0:90') echo "selected";?>>0:90</option>
<option value="0:95"<?if ($flight_duration=='0:95') echo "selected";?>>0:95</option>
<option value="100"<?if ($flight_duration=='100') echo "selected";?>>100</option>
<option value="105"<?if ($flight_duration=='105') echo "selected";?>>105</option>
<option value="110"<?if ($flight_duration=='110') echo "selected";?>>110</option>
<option value="115" <?if ($flight_duration=='115') echo "selected";?>>115</option>
</select>