Safely Grabbing Drupal Path Args

In Drupal there are system paths (not to be confused with friendly URLs) that provide information that can be used to make a page or block "self-aware".  In the example below, the user friendly path may have any one of the three example system paths.

Drupal arg structure.

 

 

 

Bad Assumption (unsafe)

<?php
   $iNID = arg(1);
?>

This will fail if this logic lands on a tag page or a custom menu hook.

Proper Treatment: Node

<?php
      if ((arg(0) == 'node') && (is_numeric(arg(1)))) {
         $iNID = arg(1);
      }
    
   //when you are ready to start using $iNID, check it for !empty() before making use of it.
?>

No notices will be thrown because arg(1) is not evaluated at all if arg(0) is not a node.

Proper Treatment Term

<?php
      if ((arg(0) == 'taxonomy') && (arg(1) == 'term') && (is_numeric(arg(2)))) {
         $iTID = arg(2);
      }
    
   //when you are ready to start using $iTID, check it for !empty() before making use of it.
?>

No notices will be thrown because arg(1) is not evaluated at all if arg(0) is not a taxonomy and arg(2) is not evaluated if arg(1) is not term.

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