How Can to convert CIDR to Netmask Addresses ??

[jalalahmadi]

Hi
I want convert CIDR to Netmask Addresses just for show to user in UI .

Code: [Select]

<select name="subnet" class="selectpicker" data-style="btn-default" data-width="auto" data-size="10" dataid="subnet">

<?php
     for ($i = 32; $i > 0; $i--):?>
   <option value="<?=$i;?>" <?=$i == $pconfig['subnet'] ? "selected=\"selected\"" : "";?>><?=$i;?></option>
<?php
                                    
endfor;?>
</select>



Please help me .

Thank you

[djGrrr]

You could use something along the lines of one of these functions:

The first one is the simplest, you can simply use it like ipv4cidr2subnet($i) to return the subnet mask

Code: (php) [Select]

<?php
function ipv4cidr2subnet($cidr) {
    static $max_ip;
    if (!isset($max_ip))
        $max_ip = ip2long('255.255.255.255');

    if ($cidr < 0 || $cidr > 32)
        return NULL;

    $subnet_long = $max_ip << (32 - $cidr);
    return long2ip($subnet_long);
}

The second is a bit more complex but will reduce execution time if displaying the list more than once per page and can be used in a foreach loop like this:
$cidr_subnets = ipv4_cidr_subnets();
foreach ($cidr_subnets as $i => $subnet):

Code: (php) [Select]

<?php
function ipv4_cidr_subnets() {
    static $subnets = [];
    if (empty($subnets)) {
        $max_ip = ip2long('255.255.255.255');
        for ($i = 0; $i <= 32; $i++)
            $subnets[$i] = long2ip($max_ip << (32 - $i));
    }

    return $subnets;
}


[jalalahmadi]

Thank you djGrrr 
This function works fine ipv4cidr2subnet  .

Code: [Select]

<?php
          for ($i = 32; $i > 0; $i--):?>
<option value="<?=$i;?>" <?=$i == $pconfig['subnet'] ? "selected=\"selected\"" : "";?>> <?= ipv4cidr2subnet($i);?>  ( /<?= $i;?> )</option>
        <?php
  endfor;?>