Age from date of birth in Drupal 7

In this tutorial I’m gonna show you how to calculate and display properly the age from a date CCK field the simplest way. The method I’m about to show you doesn’t need the Views module and if you use Views you’ll find that it’s totally compatible without adding any PHP code.

Requirements

Before starting I want you to meet the following requirements in order to follow this tutorial:

• Install and enable the Computed_field module
• Install and enable the Date module (Date API, Date & Date popup)
• Install and enable the Rules module
• Enable the core PHP filter module
• Add a date field to an existing content type (let’s call it field_dob)

For the purpose of this tutorial I created a very simple content type named Candidate with only 2 fields:

• I changed the title from Title to Full name and removed the Body field
• I added a Date field and named it field_dob

Add a computed field

Now let’s add a new field with Age as a label and field_age as a name and Computed as a field type.
In the next screen we will set the field settings:

• Computed Code (PHP):

  $entity_field[0]['value'] = ( time() - strtotime($entity->field_dob[LANGUAGE_NONE][0]['value']) ) / 86400 / 365.25;
  

• Display Code (PHP):

  $display_output = floor($entity_field_item['value']);

• Data type: Decimal
• Decimal Scale (decimal): 3

Add content and test

Now let’s add a few items and see if it works as we expected, I added a couple of entries and tested:

• Old KADIMI (born on 1 Jan 1990) => Age computed 21
• Young KADIMI (born on 2 Jan 1990) => Age computed 21

Sorting with Views

You may want to use the Views module to accommodate the output to your needs, one of the features of the Views module is that it enable you to sort results.

So what if we wanted to sort our candidates by age, Both KADIMI brothers (Old and Young) are 21 years old but Old is 1 day older that Young, for Drupal they have the same age and the result of the sorting may be inaccurate, actually we already fixed this issue by storing the age as a decimal number with 3 decimal points and displaying it as an integer (by using floor), by looking into the database table field_data_field_age with phpMyAdmin:

• Young KADIMI is 21.570 years old
• Old KADIMI is 21.573 yeas old

Update age

In order to recompute a candidate age we must re-save that candidate node, one way to do this is using Rules and Drupal cron

• Visit /admin/config/workflow/rules/reaction/add to add a rule, give it a descriptive name like “Re-save candidates nodes”
  Set React on event to: Cron maintenance tasks are performed
• Add a new action
  Set Select the action to add to: Execute custom PHP code
  Set the PHP code to:

  $old   = '1 day';      # Content is considered outdated if older than {$old}
  $type  = 'candidate';  # Apply to nodes of type {$type}
  $limit = 20;           # Update {$limit} nodes per cron
   
  $old = strtotime("now - $old");
  
  $sql = '
    SELECT n.nid FROM {node} n
    WHERE n.type = :type
      AND n.changed  < :old
    ORDER BY n.changed ASC
    LIMIT :limit
  ';
  
  $sql_vars = [
    ':type' => $type,
    ':old' => $old,
    ':limit' => $limit,
  ];
  
  $nids = db_query($sql, $sql_vars);
   
  foreach ($nids as $nid){
     $node = node_load($nid);
     node_save($node);
  }

  Tweak the 3 parameters in a way that suits your needs and that’s it!

Need help?

If you found this tutorial difficult and couldn’t follow the instructions you can ask for help on the comments section or you can hire me and I will take care of this for you.