Finding the first entry of XML and displaying it - php

Question

Im working on compiling a list using XML and PHP. I'm looking to find the first "destination tag" found in the RailVehicleStateClass for each train ID and echo it out. I tried doing a foreach loop to gather the destination tag but it just loops the same data for each train ID until the end of the xml file. Below is a snippet of the XML file, the full version has well over 700 entries and each train can have anywhere from 1 to 100+ railvehiclaes associated with it.
XML
<ScnLoader xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<trainList>
<TrainLoader>
<trainID>99991</trainID>
<TrainWasAI>false</TrainWasAI>
<DispatchTrainDirection>0</DispatchTrainDirection>
<ManuallyAppliedSpeedLimitMPH>2147483647</ManuallyAppliedSpeedLimitMPH>
<PreviousSignalInstruction>Clear</PreviousSignalInstruction>
<unitLoaderList>
<RailVehicleStateClass>
<destinationTag>TRC SVMS</destinationTag>
</RailVehicleStateClass>
<RailVehicleStateClass>
<destinationTag>PRC</destinationTag>
</RailVehicleStateClass>
</unitLoaderList>
</TrainLoader>
</trainList>
</ScnLoader>
PHP
<?php
$trains = simplexml_load_file("Auto%20Save%20World.xml") or die("Error: Cannot create object");
$totalUnitCount=0;
echo "<table>";
echo "<th>#</th>";
echo "<th>Train ID</th>";
echo "<th>Symbol</th>";
echo "<th>Direction</th>";
echo "<th>AI</th>";
foreach ($trains->xpath("//TrainLoader") as $train) {
$totalUnitCount = $totalUnitCount + 1;
foreach (array_slice($trains->xpath("//RailVehicleStateClass"),0,1) as $unit){
echo $unit->destinationTag;
}
echo "</td>";
echo "<td>";
echo $train->DispatchTrainDirection;
echo "</td>";
echo "<td>";
echo $train->TrainWasAI;
echo "</td>";
}
?>

Answer 1

Your xpath query to get the RailVehicleStateClass elements needs to be made relative to the current $train. You can do that using:
$train->xpath(".//RailVehicleStateClass")
Note the use of . in front of // to make the path relative to the current $train element.

Answer 2

First you need to use the foreach in the unitLoaderList, then you the xpath in the object you create from the foreach and add a . before the // in the query to only obtain what is inside the object.
I really don't understand what you want to accomplish with HTML table, but here is an example code that work with your file and multiple trains without HTML.
$trains = simplexml_load_file("train.xml") or die("Error: Cannot create object");
$totalUnitCount=0;
foreach ($trains->xpath("//trainList") as $train) {
$totalUnitCount = $totalUnitCount + 1;
foreach ($train->xpath(".//unitLoaderList") as $unit){
foreach ($unit->xpath(".//RailVehicleStateClass") as $railV){
echo $railV->destinationTag[0]; //Assuming all RailVehicle has at list one destination tags if not you has to another foreach with xpath of destinationTag and only get the first one
}
}
}