Magento 1.9 - get all subcategories of parent category

1) Parent category

//Parent category 
$parentCategoryId = 107;
$cat = Mage::getModel('catalog/category')->load($parentCategoryId);
$subcats = $cat->getChildren();

2) Get 1 Level sub category of Parent category.

//Get 1 Level sub category of Parent category
foreach(explode(',',$subcats) as $subCatid){
  $_category = Mage::getModel('catalog/category')->load($subCatid);
  if($_category->getIsActive()) {
    echo '
getName().'" category">'.$_category->getName().'';
   echo '
';
  }
}

3) Get 2 Level sub category of Parent sub category.

// Get 2 Level sub category of Parent sub category

foreach(explode(',',$subcats) as $subCatid)
{
  $_category = Mage::getModel('catalog/category')->load($subCatid);
  if($_category->getIsActive()) {
    echo '
getName().'" category">'.$_category->getName().'';
    $sub_cat = Mage::getModel('catalog/category')->load($_category->getId());
    $sub_subcats = $sub_cat->getChildren();
    foreach(explode(',',$sub_subcats) as $sub_subCatid){
          $_sub_category = Mage::getModel('catalog/category')->load($sub_subCatid);
          if($_sub_category->getIsActive()) {
              echo '
getName().'" category">'.$_sub_category->getName().'
';

        }
     }
     echo '
';
  }
}

4) Get 3 Level sub sub category of Parent sub sub category

// Get 3 Level sub sub category of Parent sub sub category

foreach(explode(',',$subcats) as $subCatid)
{
  $_category = Mage::getModel('catalog/category')->load($subCatid);
  if($_category->getIsActive()) {
    echo '
getName().'" category">'.$_category->getName().'';
    $sub_cat = Mage::getModel('catalog/category')->load($_category->getId());
    $sub_subcats = $sub_cat->getChildren();
    foreach(explode(',',$sub_subcats) as $sub_subCatid)
    {
          $_sub_category = Mage::getModel('catalog/category')->load($sub_subCatid);
          if($_sub_category->getIsActive()) {
              echo '
getName().'" category">'.$_sub_category->getName().'
';
              $sub_sub_cat = Mage::getModel('catalog/category')->load($sub_subCatid);
              $sub_sub_subcats = $sub_sub_cat->getChildren();
              foreach(explode(',',$sub_sub_subcats) as $sub_sub_subCatid)
              {
                $_sub_sub_category = Mage::getModel('catalog/category')->load($sub_sub_subCatid);
                if($_sub_sub_category->getIsActive()) {
                    echo '
getName().'" category">'.$_sub_sub_category->getName().'
';
                }
              }
           }
     }
     echo '
';
  }
}

 // $sub_subCatid this is sub category id . means if you want 4 level than it will take 3 level subcategory Id.

 $sub_sub_cat = Mage::getModel('catalog/category')->load($sub_subCatid);
              $sub_sub_subcats = $sub_sub_cat->getChildren();
              foreach(explode(',',$sub_sub_subcats) as $sub_sub_subCatid)
              {
                $_sub_sub_category = Mage::getModel('catalog/category')->load($sub_sub_subCatid);
                if($_sub_sub_category->getIsActive()) {
                    echo '
getName().'" category">'.$_sub_sub_category->getName().'
';
                }
              }