Configuration (Magic) Data

Warning:The API for Magic Data has been fairly significantly updated from version 3.1 to version 3.2. Although this article applies to the version 3.2 API, much of it is relevant to version 3.1. See some of the Changes

What is Magic Data?

Magic Data is a mechanism intended to handle dynamic site level configuration data. It is the basis of much of the functionality provided by the Intrahealth Informatics Core Engine (I2CE) including how pages are served and how custom reports are made.

Magic Data is a rooted tree structure with benefits. If you wish you may think of it as the analogue of the Windows Registry for your web application. You may also think of it as a nested array.

There are two parts two parts to magic data. The magic data node class, defined in I2CE/lib/I2CE_MagicDataNode and the storage mechanisms for magic data. You may use magic data without using a storage mechanism, in which case the magic data saved does on persist across sessions. By default uses the following storage mechanisms for Magic Data:

• Database: The data is stored into a table in the database. In I2CE, this is set to be the config table.
• APC: The data is stored in to a memory cache provided by apc which persists across apaches session.

As APC is faster, reads are first done from APC. If the data is not found there, it is read from the database. Data is written first to the database and then to APC.

Scalar and Non-Scalar

There are two main types of nodes scalar and a parent node

A scalar node does not have any children. It does have a value which is a possibly empty string. A scalar node can be marked as being localized. In which case the value returned depends on the localization preferences for the user.

A parent node can have as many children as it wants. Each child of a parent node must have distinct names. It does not have a value. It is not localizable.

Names and Paths

With the exception of the root node, every magic data node has a name. For a name, any numeric value is allowed. Any non-empty string is valid as long as it does not start with '__' and does contains the characters:

_-+.0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ

Absolute Paths

Magic Data nodes can be referenced by their path which is a concatenation of their names by '/.'

The root node has path '/'.

If the root node has a child with name 'some', it is referenced by the path '/some'

If some is a parent node with a child with name 'thing', then that child is referenced by the path '/some/thing'

Relative Paths

Paths can also be relative. In the example above, if you were at the node '/some' then could reference the other nodes by:

• './' references '/some'
• '../' references '/'
• './thing' references the node '/some/thing'

Defining Magic Data in Configuration Files

A convenient way to get magic data loaded into the system is to do so through a [[Technical Overview: Module Structure#Module Configuration File|module configuration file] by specifying a <configurationGroup> node after the <metadata> node.

The <configurationGroup> node is optional. If it is present it has to have the attribute name which has the same value as the module name, whhich is the name attribute in the containing <I2CEConfiguration> tag.

All magic data is relative to the path defined by the this configurationGroup. There are three options:

   * The attribute path is not present. In the following example, the magic data is stored under /modules/mercury_javascript_path. 

Example:

<configurationGroup name='mercury_javascript_popup'>
  SOME STUFF GOES HERE

</configurationGroup>

   * The attribute path is present. In the following example, the magic data is stored under /some/other/place. 

Example:

<configurationGroup name='mercury_javascript_popup' path='/some/other/place'>
  SOME STUFF GOES HERE
</configurationGroup> 

   * The module is 'I2CE'. The magic data is stored relative to /I2CE

Using Magic Data in PHP

Each node of magic data is an instance of the class I2CE_MagicDataNode. The "public variables" of a node are its child nodes which is done by making use of the __get() method. I2CE_MagicDataNode implements the RecusriveIterator, ArrayAccess, SeekableIterator, and Countable Interfaces.

I2CE has a root magic data instance which can be retrieved by:

$config=I2CE::getConfig();

Basic Access

Suppose $data is a magic data node, with a children named 'my_list' and 'amount' which are parent type and scalar type respectively. Suppose that the child node 'amount' has value 10. Suppose that there is no child named 'bad.' The children can be accessed in many ways:

Access Method	Result	Notes
$data->my_list	I2CE_MagicDataNode	This is the 'my_list' node
$data->amount	10
$data->bad	I2CE_MagicDataNode	The node did not exist, so it was created. It has an indeterminate type at the moment.
$data['my_list']	I2CE_MagicDataNode	the 'my_list' node
$data['amount']	10	the value of the 'amount' node
$data['bad']	I2CE_MagicDataNode	We created the non-existent 'bad' node and returned it

Refined Access

To get more refined access to magic data nodes you may use the traverse($path,$create=false,$return_value=true) function:

$data->traverse('my_list',false,false)	I2CE_MagicDataNode	This is the 'my_list' node
$data->traverse('bad',false,false)	null	The second argument says not to create a node that doesn't exist
$data->traverse('amount',false,false)	I2CE_MagicDataNode	The is the 'amount' node
$data->traverse('my_list',false,true)	I2CE_MagicDataNode	This is the 'my_list' node
$data->traverse('amount',false,true)	10	The value of the 'amount' node
$data->traverse('bad',false,true)	null	The second argument says not to create a node that doesn't exist
$data->traverse('my_list',true,true)	I2CE_MagicDataNode	This is the 'my_list' node
$data->traverse('amount',true,true)	10	The value of the 'amount' node
$data->traverse('bad',true,true)	I2CE_MagicDataNode	We created the non-existent 'bad' node and returned it

If a node has scalar type, you can get its value by getValue(). If you call getAsArray() on it, it will also return its value.

If a node has parent or indeterminate type, calling getValue() returns the node itself. If you call getAsArray() on it it will return a nested array. The keys at each depth are the child node's names. The values are either an array or a sting, depending on if that child is scalar or not.

Checking Existence and Type

You can use the following method to see if a Magic Data node, exists and what its type is:

• pathExists($path)
• is_scalar($path=null)
• is_parent($path=null)
• is_indeterminate($path=null)
• is_root($path=null)

Here, we the path defaults to null, the value that method is called on the node itself (this would be the same as calling it on $path='./').

You may do something like:

function set_node_to_scalar($node) {
  if (!$node instanceof I2CE_MagicDataNode) {
    echo "Why are you giving me garbage data?\n";
    return false;
  } 
  if ($node->is_scalar()) {
    echo "This node is already a scalar.  It has a value " . $node->getValue(). "\nI don't need to do anything.\n";
    return true; 
  } else {
    echo "This node is a parent node.  Although it may or may not have children, I can't set it to be scalar.\n";
    return false;
  } else{
    //$node->is_indeterminate() will return true
    echo "This node is indeterminate. Setting it to be scalar\n";
    $node->set_scalar();
    return true;
  }
}

Two other useful functions are

• getAsArray($path=null) which return the node and all of its children (recursively) as an array
• setIfIsSet(&$var,$path,$as_array=false) which will check to see if $path exists. If it does not, it returns false. If it does, it returns true and calls either getValue() or getAsArray() on the node referred to by the path.

Child Names and Iterators

To get the names of the child nodes of a node, we use the getKeys() method. Suppose that we magic data set up as follows:

Path	Type	Value
/	parent	NONE
/color	scalar	green
/modules	parent	NONE
/modules/modA	parent	NONE
/modules/modB	parent	NONE
/modules/modA/favorite_clay_animation	scalar	Mr. Bill

You may also something similar as:

echo "I like the color " . $config->color . "\n";
$keys = $config->getKeys();
foreach ($keys as $key) {
  if ($config->is_parent($key)) {
    echo "The node named $key under at " . $config->getPath(false) . " is a parent node.  It has children " . implode(',', $config->$key->getKeys()) . ".\n";
  } else if ($config->is_scalar($key)) {
   echo "The node named $key under at " . $config->getPath(false) . " is a scalar with value " . $config->$key ".\n";
  }
}

which would result in:

I like the color red.
The node named modules under / is a parent node.  It has children modA,modB.
The node named color under / is a scalar node with value red.

As a magic data node is an iterator, we can do things like:

foreach ($config as $key=>$node) {
  if ($node instanceof I2CE_MagicDataNode) {
   echo "The node named $key under at " . $config->getPath(false) . " is a parent node.  It has children " . implode(',', $node->getKeys()) . ".\n";
  } else {
   echo "The node named $key under at " . $config->getPath(false) . " is a scalar with value " . $node .".\n";
  }
}

which would result in:

The node named modules under / is a parent node.  It has children modA,modB.
The node named color under / is a scalar node with value red.

or:

$modules = $config->modules;
foreach ($modules as $module=>$data) {
  if ($data->is_scalar('favorite_clay_animation')) {
     echo "The module $module thinks " . $data->favorite_clay_animation . " is a super star!\n";
  }
}

would result in:

 The module modA things Mr. Bill is a super star!

Changes from 3.1

• Removed the __ from method calls.
• Relaxed the rules for the names of Magic Data nodes.
• Implemented the various interfaces
• Added in support for localization of values