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using data from child element to select data in other element using simplexml in php

So, I'm using simplexml in php to display elements from an xml file onto a webpage. This is working fine when selecting a whole list child elements in one certain element. The thing is however, I need to select a number of rules in one element, and display the data attached to these certain rules found in another element.

To clarify, this a simplified version of my xml file (it contains everything I need):

<report>
    <profile_info>  
    <rules>

        <rule id="RUL1">
            <display_name>
            XMP does not have CreateDate entry in the XMP Basic Schema
            </display_name>
            <display_comment>
            This entry of the predefined XMP Basic Schema defines the date and time when the document has been created. It is required by some PDF-based ISO standards.
            </display_comment>
        </rule>

        <rule id="RUL133">
            <display_name>
            XMP does not have a VersionID entry in the XMP Media Management Schema
            </display_name>
            <display_comment>
            The VersionID in the XMP Media Management Schema (xmpMM) is the version identifier for respective resource. This entry is required by some PDF-based ISO standards for file identification.
            </display_comment>
        </rule>

        <rule id="RUL169">
            <display_name>
            Page does not have TrimBox or ArtBox
            </display_name>
            <display_comment>
            Either ArtBox or TrimBox should be defined for pages in a PDF file that are used in prepress. PDF/X ISO standards require the presence of one of these boxes.
            </display_comment>
        </rule>

    </rules>
</profile_info>


<results>
    <hits rule_id="RUL169" severity="Error">
    </hits>
    <hits rule_id="RUL133" severity="Error">
    </hits>
</results>
</report>

So far, I'm able to echo the entire list of rules with their display_name and display_comment using simplexml inside of php.

This is not what I want however. I want to be able to only show the child elements of the rules that actually gave an error, as displayed in the root element "results".

To sum up my problem: take the id's of the rules that gave an error in <results> and use those to display the display_name and display_comment shown in <rules>, another root element.

This the php code I have so far to list the entire list of rules that works, if that is of any help. (this works, but this is not what I want btw)

<?php

    if(file_exists('../uploads/reports/report.xml')){
    $xml = simplexml_load_file('../uploads/reports/report.xml');
    } 
    else{
    exit('Could not load the file ...');
    }

foreach ($xml->profile_info as $profile_info){
    foreach ($profile_info->rules as $rules){
        foreach ($rules->rule as $rule){

                echo '<div id="name">'.$rule->display_name.'</div>'.'<div id="comment">'.$rule
                    ->display_comment.'</div>';
?>

Thanks in advance!

Solution

  • The solution using SimpleXMLElement::xpath and array_map functions:

    $xml = simplexml_load_file('../uploads/reports/report.xml');
...
$hits = $xml->xpath("results/hits/@rule_id");
$ruleIds = array_map(function($v){    // getting search path for each needed rule
    return "profile_info/rules/rule[@id='". (string)$v. "']"; 
}, $hits);

foreach ($xml->xpath(implode(" | ", $ruleIds)) as $rule) {
    echo '<div id="name">'. $rule->display_name .'</div>'.
         '<div id="comment">'. $rule->display_comment .'</div>';
}

    The "view-source" output: 

            <div id="name">
        XMP does not have a VersionID entry in the XMP Media Management Schema
        </div><div id="comment">
        The VersionID in the XMP Media Management Schema (xmpMM) is the version identifier for respective resource. This entry is required by some PDF-based ISO standards for file identification.
        </div><div id="name">
        Page does not have TrimBox or ArtBox
        </div><div id="comment">
        Either ArtBox or TrimBox should be defined for pages in a PDF file that are used in prepress. PDF/X ISO standards require the presence of one of these boxes.
        </div>