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<?php
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/*
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============================================================================================
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Filename: 
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---------
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xml2json.php
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Description: 
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------------
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This PHP class converts XML-based data into JSON formatted data. 
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This program makes use of several open source PHP utility classes and functions.
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License:
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--------
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This code is made available free of charge with the rights to use, copy, modify,
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merge, publish and distribute. This Software shall be used for Good, not Evil.
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First Created on:
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-----------------
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Oct/04/2006
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Last Modified on:
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-----------------
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Oct/07/2006
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============================================================================================
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*/
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require_once 'json/JSON.php';
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// Internal program-specific Debug option.
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define ("DEBUG", false);
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// Maximum Recursion Depth that we can allow.
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define ("MAX_RECURSION_DEPTH_ALLOWED", 25);
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// An empty string
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define ("EMPTY_STR", "");
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// SimpleXMLElement object property name for attributes
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define ("SIMPLE_XML_ELEMENT_OBJECT_PROPERTY_FOR_ATTRIBUTES", "@attributes");
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// SimpleXMLElement object name.
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define ("SIMPLE_XML_ELEMENT_PHP_CLASS", "SimpleXMLElement");
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class xml2json {
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	/*   
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	=============================================================================
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	Function name:
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	---------------
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	transformXmlStringToJson
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	Function Parameters: 
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	---------------------
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	1) XML data string.
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	Description:
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	------------
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	This function transforms the XML based String data into JSON format. If the input XML
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	string is in table format, the resulting JSON output will also be in table format.
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	Conversely, if the input XML string is in tree format, the resulting JSON output will
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	also be in tree format.
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	Function Return Value:
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	----------------------
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	1) If everything is successful, it returns a string containing JSON table/tree formatted data. 
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	Otherwise, it returns an empty string.
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	First Created on:
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	-----------------
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	Oct/04/2006
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	Last Modified on:
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	-----------------
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	Oct/07/2006  	
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	=============================================================================
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	*/	
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	public static function transformXmlStringToJson($xmlStringContents) {
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		/*
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		Get the SimpleXMLElement representation of the function input 
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		parameter that contains XML string. Convert the XML string 
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		contents to SimpleXMLElement type. SimpleXMLElement type is 
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		nothing but an object that can be processed with normal property 
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		selectors and (associative) array iterators.
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		simplexml_load_string returns a SimpleXMLElement object which 
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		contains an instance variable which itself is an associative array of 
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		several SimpleXMLElement objects.	
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		*/
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		$simpleXmlElementObject = simplexml_load_string($xmlStringContents);
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		if ($simpleXmlElementObject == null) {
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			return(EMPTY_STR);
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		}
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		$simpleXmlRootElementName = $simpleXmlElementObject->getName();
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		// Uncomment this line to see the inner details of the SimpleXMLElement object.
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		if (DEBUG) {
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			// var_dump($simpleXmlRootElementName);
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			// var_dump($simpleXmlElementObject);
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		}	
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		$jsonOutput = EMPTY_STR;		
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		// Let us convert the XML structure into PHP array structure.
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		$array1 = xml2json::convertSimpleXmlElementObjectIntoArray($simpleXmlElementObject);
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		if (($array1 != null) && (sizeof($array1) > 0)) {		
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			//create a new instance of Services_JSON
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			$json = new Services_JSON();
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			$jsonOutput = $json->encode($array1);
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			if (DEBUG) {
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				// var_dump($array1);
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				// var_dump($jsonOutput);
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			}	
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		} // End of if (($array1 != null) && (sizeof($array1) > 0))
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		return($jsonOutput);					
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	} // End of function transformXmlStringToJson
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	/*   
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	=============================================================================
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	Function name:
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	---------------
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	convertSimpleXmlElementObjectIntoArray
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	Function Parameters: 
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	---------------------
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	1) Simple XML Element Object
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	(The following function argument needs to be passed only when this function is 
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	called recursively. It can be omitted when this function is called from another
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	function.)
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	2) Recursion Depth
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	Description:
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	------------
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	This function accepts a SimpleXmlElementObject as a single argument. 
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	This function converts the XML object into a PHP associative array. 
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	If the input XML is in table format (i.e. non-nested), the resulting associative 
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	array will also be in a table format. Conversely, if the input XML is in 
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	tree (i.e. nested) format, this function will return an associative array 
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	(tree/nested) representation of that XML.
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	There are so many ways to turn an XML document into a PHP array. Out of all
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	those options, the recursive logic here uses a method that is very nicely 
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	documented by the PHP open source community in the SimpleXMLElement section of 
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	the PHP manual available at www.php.net. Credit goes to all those kind 
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	PHP (People Helping People!!!) souls.
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	Function Return Value:
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	----------------------
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	1) If everything is successful, it returns an associate array containing 
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	the data collected from the XML format. Otherwise, it returns null.
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	Caution and Remarks:
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	---------------------
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	IT IS A RECURSIVE FUNCTION.
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	First Created on:
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	-----------------
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	Oct/04/2006
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	Last Modified on:
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	-----------------
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	June/01/2007  	
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	=============================================================================
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	*/		
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	public static function convertSimpleXmlElementObjectIntoArray($simpleXmlElementObject, &$recursionDepth=0) {		
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		// Keep an eye on how deeply we are involved in recursion.
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		if ($recursionDepth > MAX_RECURSION_DEPTH_ALLOWED) {
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			// Fatal error. Exit now.
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			return(null);
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		}
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		if ($recursionDepth == 0) {
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			if (get_class($simpleXmlElementObject) != SIMPLE_XML_ELEMENT_PHP_CLASS) {
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				// If the external caller doesn't call this function initially  
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				// with a SimpleXMLElement object, return now.				
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				return(null);				
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			} else {
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				// Store the original SimpleXmlElementObject sent by the caller.
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				// We will need it at the very end when we return from here for good.
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				$callerProvidedSimpleXmlElementObject = $simpleXmlElementObject;
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			}
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		} // End of if ($recursionDepth == 0) {		
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		if (get_class($simpleXmlElementObject) == SIMPLE_XML_ELEMENT_PHP_CLASS) {
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			// Get a copy of the simpleXmlElementObject
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			$copyOfsimpleXmlElementObject = $simpleXmlElementObject;
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      		// Get the object variables in the SimpleXmlElement object for us to iterate.
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       		$simpleXmlElementObject = get_object_vars($simpleXmlElementObject);
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	   	}		
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       	// It needs to be an array of object variables.
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   		if (is_array($simpleXmlElementObject)) {
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   			// Initialize the result array.
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   			$resultArray = array();
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       		// Is the input array size 0? Then, we reached the rare CDATA text if any.
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   			if (count($simpleXmlElementObject) <= 0) {
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   				// Let us return the lonely CDATA. It could even be whitespaces.
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   				return (trim(strval($copyOfsimpleXmlElementObject)));
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   			}
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   			// Let us walk through the child elements now.
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       		foreach($simpleXmlElementObject as $key=>$value) {
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       			// When this block of code is commented, XML attributes will be
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       			// added to the result array. 
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       			// Uncomment the following block of code if XML attributes are  
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       			// NOT required to be returned as part of the result array.       			
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       			/*
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  	     		if((is_string($key)) && ($key == SIMPLE_XML_ELEMENT_OBJECT_PROPERTY_FOR_ATTRIBUTES)) {
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  	     			continue;
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       			}
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       			*/
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       			// Let us recursively process the current element we just visited.
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				// Increase the recursion depth by one.
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				$recursionDepth++;	       			
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           		$resultArray[$key] = xml2json::convertSimpleXmlElementObjectIntoArray($value, $recursionDepth);
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           		// Decrease the recursion depth by one.
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           		$recursionDepth--;
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       		} // End of foreach($simpleXmlElementObject as $key=>$value) {		
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       		if ($recursionDepth == 0) {
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				// That is it. We are heading to the exit now.
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				// Set the XML root element name as the root [top-level] key of 
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				// the associative array that we are going to return to the caller of this
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				// recursive function.
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				$tempArray = $resultArray;
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				$resultArray = array();
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				$resultArray[$callerProvidedSimpleXmlElementObject->getName()] = $tempArray;
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       		}
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       		return ($resultArray);
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   		} else {
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   			// We are now looking at either the XML attribute text or 
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   			// the text between the XML tags.
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   			return (trim(strval($simpleXmlElementObject)));
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   		} // End of else
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	} // End of function convertSimpleXmlElementObjectIntoArray. 
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} // End of class xml2json
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