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XML XPath Query on multiple attributes in PHP

Posted on 2010-09-21
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Last Modified: 2012-05-10
I have the following XML file..

<?xml version="1.0"?>
<events>
  <tag user="168" show="shows.xml" touch="1285133609" name="special_event" created="1285131987"/>
  <tag user="168" show="media.xml" touch="1285135678" name="special_event" created="1285132134"/>
</events>

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I can use xpath like this to grab an attribute fine... count($results) = 2

$results = $xml->xpath('/events/tag[@user=168]');

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but I want to grab two attributes, at the same time and look for an exact match on both cases
i thought i could do it like this but doesn't work?

$results = $xml->xpath('/events/tag[@user=168] and /events/tag[@show=show.xml]');

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Anyone got an idea where I've gone wrong?

Thx
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Question by:edjent
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7 Comments
 
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Expert Comment

by:hernst42
ID: 33732148
Try:
$results = $xml->xpath('/events/tag[@user=168 and @show=show.xml]');

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Expert Comment

by:hernst42
ID: 33732151
additional it should be @show=shows.xml for the given xml
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Accepted Solution

by:
Geert Bormans earned 500 total points
ID: 33732215
small note on hernst42's suggestion

> $results = $xml->xpath('/events/tag[@user=168 and @show=show.xml]');

That is exactly the way you could do this
BUT
@show = show.xml
will look for the element <show.xml> to be equal to the content of the attribute
you mean a string, so you will need quotes

$results = $xml->xpath('/events/tag[@user=168 and @show="shows.xml"]');

I usually do this, doesn't make much of a difference

$results = $xml->xpath('/events/tag[@user=168][@show="shows.xml"]');
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LVL 109

Expert Comment

by:Ray Paseur
ID: 33733443
SimpleXML can give you an array of objects.  This makes it VERY easy to use an iterator.  Here is how I solve the problem.  Best to all, ~Ray
<?php // RAY_xml_example_243.php
error_reporting(E_ALL);

// TEST DATA FROM THE POST AT EE MODIFIED TO INCLUDE ONE DUPLICATED ATTRIBUTE COMBINATION
$xml = <<<EOXML
<?xml version="1.0"?>
<events>
  <tag user="168" show="shows.xml" touch="1285133609" name="special_event" created="1285131987"/>
  <tag user="168" show="books.xml" touch="1285135678" name="special_event" created="1285132134"/>
  <tag user="168" show="media.xml" touch="1285135678" name="special_event" created="1285132134"/>
  <tag user="168" show="books.xml" touch="1285135678" name="special_event" created="1285132134"/>
</events>
EOXML;

// MAKE AN OBJECT
$obj = SimpleXML_Load_String($xml);

// VISUALIZE THE OBJECT
echo "<pre>" .  PHP_EOL;
var_dump($obj);

// USE AN ITERATOR TO LOOK A THE OBJECT
$arr = array();
foreach ($obj as $key => $tag)
{
    // EXTRACT ATTRIBUTES FROM THE TAGS
    $u = $tag["user"];
    $s = $tag["show"];
    echo PHP_EOL . "$u $s";

    // IDENTIFY REPLICATED ATTRIBUTE COMBINATIONS
    if (in_array($u.$s, $arr)) echo " DUPLICATE";
    $arr[] = $u.$s;
}

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Author Comment

by:edjent
ID: 33741363
I really didn't want to iterate through the values as this sheet will end up being really long over time. xpath seems much quicker option.

I used the expressions above in researching but I wasn't able to get the 'and' operator to work correctly or by stacking the vars [@1][@2], least so it appeared.

Gertone nailed it show.xml is a string, to be compared. I failed purely without the "" as it wouldn't match! pure late night oversight!

doh! thanks guys
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Expert Comment

by:Geert Bormans
ID: 33741432
welcome
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Expert Comment

by:Ray Paseur
ID: 33742878
Regarding this" "I really didn't want to iterate through the values as this sheet will end up being really long over time. xpath seems much quicker option."

You might want to test the relative speed of the processes.  How do you think Xpath finds things?  It's not magic, and it does not know where they are in advance.  It uses its own iterators and comparisons.  It may take millions of iterations before you see a second or two of difference between the coding methods.  Nothing wrong with using Xpath, but I find there is more control in the iterators.  It's just my preference.

 When the only tool you have is a hammer, everything looks like a nail ;-)

Good luck with your project, ~Ray
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