<form method=post>
<input type=text name=number value="10">
<input type=submit value="yaratish">
<form>

<?php
echo generate_password($_POST['number']);
function generate_password($number) {
    $arr = array(
    'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','r','s','t','u','v','x','y','z',
    'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','R','S','T','U','V','X','Y','Z',
    '1','2','3','4','5','6','7','8','9','0');
    // Parol yaratimiz
    $pass = "";
    for($i = 0; $i < $number; $i++) {
        // Biz tasodifiy array indeksini hisoblash
        $index = rand(0, count($arr) - 1);
        $pass .= $arr[$index];
    }
    return $pass;
}
?>

<form method=post>
<input type=text name=number value="10">
<input type=submit value="yaratish">
<form>

<?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>