SimpleXMLElement - Trying to get property of non-object - php

Question

In a response we receive an xml file, then convert to SimpleXMLElement, then access the elements and attributes as needed. However, we are getting "Trying to get property of non-object" when xml is loaded directly from string response vs from saved response.
//This code works
$response = simplexml_load_file( "response.xml" );
var_dump($response);
echo $response->RESPONSE->RESPONSE_DATA->FILE_INFORMATION['Order_Number'];
//Returns
//object(SimpleXMLElement)#153 (4) { ["#attributes"]=> array(1)...the rest of the xml file...
//Order_Number
//This code returns error
$response = simplexml_load_string( $response );
var_dump($response);
echo $response->RESPONSE->RESPONSE_DATA->FILE_INFORMATION['Order_Number'];
//Returns
//object(SimpleXMLElement)#153 (1) { [0]=> string(33864) "" }
//Notice: Trying to get property of non-object in...
What would cause the xml to fail when using simplexml_load_string instead of simplexml_load_file?
Here is a snippet of the xml file:
<?xml version="1.0" encoding="UTF-8"?>
<RESPONSE_GROUP>
<RESPONSE>
<RESPONSE_DATA>
<FILE_INFORMATION Order_Number="19222835">
...
</FILE_INFORMATION>
</RESPONSE_DATA>
</RESPONSE>
</RESPONSE_GROUP>

Answer 1

You've just overlooked a little detail here. It is correct what you say for the first part:
$response = simplexml_load_file( "response.xml" );
This loads the XML document from the file. However when you look at the second part:
$response = simplexml_load_string( $response );
You don't load from string response. $response represents the SimpleXMLElement you've just created from file. The more "correct" example is:
$buffer = file_get_contents( "response.xml" );
$response = simplexml_load_string( $buffer );
You perhaps just were confused due to variable-reuse (taken the same named variable for two different things).
And better as var_dump is to check with $response->asXML() as it will show you the document as XML which shows better what you have (or not).

Answer 2

This works for me:
<?php
$response = '<?xml version="1.0" encoding="UTF-8"?>
<RESPONSE_GROUP>
<RESPONSE>
<RESPONSE_DATA>
<FILE_INFORMATION Order_Number="19222835">
...
</FILE_INFORMATION>
</RESPONSE_DATA>
</RESPONSE>
</RESPONSE_GROUP>';
//This code returns error
$response = simplexml_load_string( $response );
var_dump($response);
echo $response->RESPONSE->RESPONSE_DATA->FILE_INFORMATION['Order_Number'];
?>
Output:
object(SimpleXMLElement)#1 (1) {
["RESPONSE"]=>
object(SimpleXMLElement)#2 (1) {
["RESPONSE_DATA"]=>
object(SimpleXMLElement)#3 (1) {
["FILE_INFORMATION"]=>
string(33) "
...
"
}
}
}
19222835