Get all IP v4 addresses of server - PHP Snippet

This php function list all IP v4 addresses of the server/machine where script is executed. It works on Windows, Ubuntu and MacOSX.

function get_ipv4_addresses() { 
    $interfaces = array(); 
    $regexp = '([\d]{1,3}\.[\d]{1,3}\.[\d]{1,3}\.[\d]{1,3})'; 
    $os = strtoupper(PHP_OS); 
    if ($os === 'WINNT') { 
      $buffer = shell_exec('ipconfig'); 
      $pattern = "/IPv4 Address[^:]+: $regexp/"; 
    } else { 
      $buffer = shell_exec('ifconfig'); 
      $pattern = "/inet addr:\s*$regexp/"; 
    } 
    if (preg_match_all($pattern, $buffer, $matches)) { 
        $interfaces = $matches[1]; 
    } 
    return $interfaces;