<?php
$necha = isset($_POST['son']) ? trim($_POST['son']) : ''; 
 
 
echo '<b>Parol qancha belgi bo\'lsin</b>? <select name="son">';
for ($i = 6; $i < 12; $i++) { 
echo '<option name="son" value="'.$i.'" '.($necha == $i ? ' selected="selected"' : '').'> '.$i.' </option>';  
}
?>

<form method=post>
<input type=text name=number value="'.$necha.'"?
<input type=submit value="yaratish">
<form>