Comparing values of 2 xml files and echoing match - php

Question

I'm trying to use 2 xml files to put data on to a list. One Xml file is not editable by me the 2nd is a reference database of sorts that I created. Both files have a common string for <rvXMLfilename> and if both xml file strings match I want to echo out a string from XML file 2. I attmepted to write this in my php script but I could not get it to work.
$railunit = simplexml_load_file('railUnitList.xml');
$orders = simplexml_load_file('train.xml');
foreach ($orders->xpath("//RailVehicleStateClass") as $traininfo):
$rvXMLfilename=$traininfo->rvXMLfilename;
$unitType=$traininfo->unitType;
$unitNumber=$traininfo->unitNumber;
$destinationTag=$traininfo->destinationTag;
$loadWeightUSTons=$traininfo->loadWeightUSTons;
echo "<tr>";
echo "<td>";
if($railunit->rvXMLfilename == $orders->rvXMLfilename){
echo $railunit->unitType;
}else{
echo "error!";
}
XML File 1
<?xml version="1.0"?>
<ScnLoader xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<trainList>
<TrainLoader>
<unitLoaderList>
<RailVehicleStateClass>
<rvXMLfilename>R8_SD40T-2_UP03.xml</rvXMLfilename>
<unitType>US_DieselEngine</unitType>
<loadWeightUSTons>14.2985783</loadWeightUSTons>
<destinationTag>MDTLA</destinationTag>
<unitNumber>8626</unitNumber>
</RailVehicleStateClass>
<RailVehicleStateClass>
<rvXMLfilename>R8_SD40T-2_UP01.xml</rvXMLfilename>
<unitType>US_DieselEngine</unitType>
<loadWeightUSTons>14.2985792</loadWeightUSTons>
<destinationTag>None</destinationTag>
<unitNumber>4401</unitNumber>
</RailVehicleStateClass>
<RailVehicleStateClass>
<rvXMLfilename>R8_SD40T-2_UP01.xml</rvXMLfilename>
<unitType>US_DieselEngine</unitType>
<loadWeightUSTons>14.2985783</loadWeightUSTons>
<destinationTag>None</destinationTag>
<unitNumber>4454</unitNumber>
</RailVehicleStateClass>
</unitLoaderList>
</TrainLoader>
</trainList>
</ScnLoader>
XML File 2
<railUnitList>
<railUnit>
<rvXMLfilename>R8_SD40T-2_UP01.xml</rvXMLfilename>
<unitType>SD40-2T Locomotive</unitType>
<reportingMark>UP</reportingMark>
<axelCount>6</axelCount>
<unitWeight></unitWeight>
<unitLength>71</unitLength>
</railUnit>
<railUnit>
<rvXMLfilename>R8_CoveredHopper_ACF2970_BN01.xml</rvXMLfilename>
<unitType>Covered Hopper</unitType>
<reportingMark>BN</reportingMark>
<axelCount>4</axelCount>
<unitWeight></unitWeight>
<unitLength>60</unitLength>
</railUnit>
<railUnit>
<rvXMLfilename>R8_C14Hopper_POTASH01.xml</rvXMLfilename>
<unitType>Covered Hopper</unitType>
<reportingMark>POTX</reportingMark>
<axelCount>4</axelCount>
<unitWeight></unitWeight>
<unitLength>60</unitLength>
</railUnit>
<railUnit>
<rvXMLfilename>Run8_Tank107BN01.xml</rvXMLfilename>
<unitType>Tank</unitType>
<reportingMark>BN</reportingMark>
<axelCount>4</axelCount>
<unitWeight></unitWeight>
<unitLength>59</unitLength>
</railUnit>
</railUnitList>

Answer 1

There are a couple of issues with your code. Firstly you cannot directly refer to the value of a SimpleXMLElement as e.g. $rvXMLfilename=$traininfo->rvXMLfilename; you need to cast it to the appropriate type. Secondly rvXMLfilename is not a child of $railunit. I think you probably want to iterate through the values in your $railunit, comparing each of them with the values you extract from the $orders XML. This code should achieve what you want:
foreach ($orders->xpath("//RailVehicleStateClass") as $traininfo) {
$rvXMLfilename=(string)$traininfo->rvXMLfilename;
$unitType=(string)$traininfo->unitType;
$unitNumber=(int)$traininfo->unitNumber;
$destinationTag=(string)$traininfo->destinationTag;
$loadWeightUSTons=(float)$traininfo->loadWeightUSTons;
echo "<tr>";
echo "<td>";
$message = "error!";
foreach ($railunit->railUnit as $ru) {
if((string)$ru->rvXMLfilename == $rvXMLfilename){
$message = (string)$ru->unitType;
}
}
echo $message;
}
Output (for your sample data)
<tr><td>error!<tr><td>SD40-2T Locomotive<tr><td>SD40-2T Locomotive

Answer 2

Again use the XPath query to get the values you're looking for. Stick all the filenames into an array, for easier comparison later.
<?php
$railunit = simplexml_load_file('railUnitList.xml');
$orders = simplexml_load_file('train.xml');
foreach ($railunit->railUnit as $railunit) {
$key = (string)$railunit->unitType;
$value = (string)$railunit->rvXMLfilename;
$filenames[$key] = $value;
}
foreach ($orders->xpath("//RailVehicleStateClass") as $traininfo) {
$rvXMLfilename=$traininfo->rvXMLfilename;
$unitType=$traininfo->unitType;
$unitNumber=$traininfo->unitNumber;
$destinationTag=$traininfo->destinationTag;
$loadWeightUSTons=$traininfo->loadWeightUSTons;
echo "<tr>";
echo "<td>";
if(in_array($traininfo->rvXMLfilename, $filenames)){
echo array_search($traininfo->rvXMLfilename, $filenames);
} else {
echo "error!";
}
}
Note also your use of $orders->rvXMLfilename in the original code. The PHP structure is the same as the XML structure, you can't reference an element in that fashion unless it's the direct child of the root element.