$final_width_of_image = 500;
$path_to_image_directory = $_SERVER['DOCUMENT_ROOT']."/images/full/";
$path_to_thumbs_directory = $_SERVER['DOCUMENT_ROOT']"/images/thumbs/";

$extension = strtolower(substr(strrchr($_FILES['avatar']['name'], '.'), 1));
if(trim($extension)){
$filename = substr(md5(microtime() . rand(0, 9999)), 0, 20) .'_avatar.'. $extension;
$source = $_FILES['avatar']['tmp_name'];
    if(preg_match('/.+.(jpe?g|png|gif)/is', $_FILES['avatar']['name'])){
       if($_FILES['avatar']['size'] != 0 AND $_FILES['avatar']['size']<=10000000){
        $target = $path_to_image_directory . $filename;
        if(move_uploaded_file($source, $target)){
          //Добавление в базу
        }
     }
  }