get all subcategories of parent category magento

By default magento does not provide the subcategory of the parent categories. if you want to show sub categories of parent categories in magento than simple follow below step.


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

?>

// Get 1 Level sub category of Parent category.

<?php 

foreach(explode(',',$subcats) as $subCatid)
              {
                $_category = Mage::getModel('catalog/category')->load($subCatid);
  if($_category->getIsActive()) {
    echo '<ul><a href="'.$_category->getURL().'" title="View the products for the "'.$_category->getName().'" category">'.$_category->getName().'</a>';
   echo '</ul>';
  }
}

?>

// Get 2 Level sub category of Parent sub category

<?php 
foreach(explode(',',$subcats) as $subCatid)
{
  $_category = Mage::getModel('catalog/category')->load($subCatid);
  if($_category->getIsActive()) {
    echo '<ul><a href="'.$_category->getURL().'" title="View the products for the "'.$_category->getName().'" category">'.$_category->getName().'</a>';
    $sub_cat = Mage::getModel('catalog/category')->load($_category->getId());
    $sub_subcats = $sub_cat->getChildren();
    foreach(explode(',',$sub_subcats) as $sub_subCatid)
    {
          $_sub_category = Mage::getModel('catalog/category')->load($sub_subCatid);
          if($_sub_category->getIsActive()) {
              echo '<li class="sub_cat"><a href="'.$_sub_category->getURL().'" title="View the products for the "'.$_sub_category->getName().'" category">'.$_sub_category->getName().'</a></li>';

 }
     }
     echo '</ul>';
  }
}
?>

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

<?php 
foreach(explode(',',$subcats) as $subCatid)
{
  $_category = Mage::getModel('catalog/category')->load($subCatid);
  if($_category->getIsActive()) {
    echo '<ul><a href="'.$_category->getURL().'" title="View the products for the "'.$_category->getName().'" category">'.$_category->getName().'</a>';
    $sub_cat = Mage::getModel('catalog/category')->load($_category->getId());
    $sub_subcats = $sub_cat->getChildren();
    foreach(explode(',',$sub_subcats) as $sub_subCatid)
    {
          $_sub_category = Mage::getModel('catalog/category')->load($sub_subCatid);
          if($_sub_category->getIsActive()) {
              echo '<li class="sub_cat"><a href="'.$_sub_category->getURL().'" title="View the products for the "'.$_sub_category->getName().'" category">'.$_sub_category->getName().'</a></li>';
              $sub_sub_cat = Mage::getModel('catalog/category')->load($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($_sub_sub_category->getIsActive()) {
                    echo '<li class="sub_cat"><a href="'.$_sub_sub_category->getURL().'" title="View the products for the "'.$_sub_sub_category->getName().'" category">'.$_sub_sub_category->getName().'</a></li>';
                }
              }
           }
     }
     echo '</ul>';
  }
}

?>



If you want 4th, 5th,.... or n level category and so on sub categories than simple add this script.
Note:- For n level category please use recursion


<?php 

 // $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($_sub_sub_category->getIsActive()) {
                    echo '<li class="sub_cat"><a href="'.$_sub_sub_category->getURL().'" title="View the products for the "'.$_sub_sub_category->getName().'" category">'.$_sub_sub_category->getName().'</a></li>';
                }
              }

?>