php and xml

I'm needing to modify the value of  a specific XML node with php, but I keep getting this error with the following code:

Catchable fatal error: Argument 1 passed to DOMNode::replaceChild() must be an instance of DOMNode, string given in...


      /*Here's the XML Structure:*/
<pages>
	<page>
		<contents>A bunch of text here
		</contents>
	</page>
	<page>
		<contents>A bunch of text here
		</contents>
	</page>
	<page>
		<contents>A bunch of text here
		</contents>
	</page>
</pages>

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/*And here's the code I'm trying to use to edit specific content nodes*/
	$data = new DOMDocument('1.0', 'utf-8');
	$data->formatOutput = true;
	$data->preserveWhiteSpace = true;
	$data->load('../data.xml');
	
	//load elements

	$page = $data->getElementsByTagName('page')->item(0);
	$contents = $page->getElementsByTagname('contents')->item(0);
	
	$contents = $string; //This is a string variable

	$page->replaceChild($contents, $contents);  //This is the line that produces the error

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So I'm not sure if my overall approach is wrong, or if I just need to modify the string variable make it an instance of DOMNode.  Please Help!  Thank you!
KaiserOwnerAsked:
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aikimarkCommented:
Once you execute this statement:
$contents = $string; //This is a string variable

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$contents no longer points to the node.

Delete or comment that statement and try this version of the replaceChilld() statement.
$page->replaceChild($contents, $string);  //This is the line that produces the error

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duncanb7Commented:
Please read the manual and  example  for replaceChild() in php.net, it is used to replace it to
new node at http://php.net/manual/en/domnode.replacechild.php



Duncan
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duncanb7Commented:
Try  this
$data = new DOMDocument('1.0', 'utf-8');
	$data->formatOutput = true;
	$data->preserveWhiteSpace = true;
	$data->load('../data.xml');
	
	//load elements

	$page = $data->getElementsByTagName('page')->item(0);
	$contents = $page->getElementsByTagname('contents')->item(0);
$contents->nodeValue=$string;

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0
Ray PaseurCommented:
This looks like a very theoretical and redacted example.  It may be helpful if you have a better test case.  But that aside, here is how you can do it.  Please copy this, install it on your server and run it to see the output, and please post back if you still have any questions.  Best regards, ~Ray

<?php // demo/temp_kwkened.php
error_reporting(E_ALL);
echo '<pre>';

// SEE http://www.experts-exchange.com/Programming/Languages/Scripting/PHP/Q_28486615.html

$xml = <<<EOD
<pages>
	<page>
		<contents>A bunch of text here
		</contents>
	</page>
	<page>
		<contents>A bunch of text here
		</contents>
	</page>
	<page>
		<contents>A bunch of text here
		</contents>
	</page>
</pages>
EOD;

// LOAD THE XML INTO AN OBJECT
$obj = SimpleXML_Load_String($xml);

// REPLACE SOMETHING IN THE OBJECT
$obj->page[0]->contents = 'New data' . PHP_EOL. "\t\t";

// RECOVER THE XML FROM THE OBJECT
$new = $obj->asXML();

// RENDER THE OLD XML AND THE MUTATED XML
echo htmlentities($xml);
echo PHP_EOL;

echo htmlentities($new);
echo PHP_EOL;

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