Foreach loop with xPath on SimpleXML object returning duplicate data

Question

Can anyone help explain to me why the following is returning duplicate data?

<?php
$xml_test = '<array key="results">
    <array key="123">
        <string key="mask">1234</string>
    </array>
    <array key="987">
        <string key="mask">5678</string>
    </array>
</array>';

$load_test = simplexml_load_string($xml_test);

foreach ($load_test as $array)
{
    $mask = $array->xpath('//string[@key="mask"]');

    print 'Mask: ' . $mask[0] . '<br />';
}

Returns:

Mask: 1234
Mask: 1234

If I throw a print_r($array) within the foreach loop, I get:

SimpleXMLElement Object
(
    [@attributes] => Array
        (
            [key] => 123
        )

    [string] => 1234
)
Mask: 1234

SimpleXMLElement Object
(
    [@attributes] => Array
        (
            [key] => 987
        )

    [string] => 5678
)
Mask: 1234

What the hell is going on? Why am I getting duplicate masks when I use an xPath expression when both of the $array quite clearly are not holding duplicate data.

Michael Berkowski · Accepted Answer · 2012-03-11 12:55:09Z

3

You are making the same xpath query twice, once for each of the <array> nodes in your XML. There is no need for the outer loop. Just do your xpath query, then loop over its results.

$mask = $array->xpath('//string[@key="mask"]');
print 'Mask: ' . $mask[0] . '<br />';
print 'Mask: ' . $mask[1] . '<br />';

Or do the xpath query first, then loop over it:

$mask = $array->xpath('//string[@key="mask"]');
foreach ($mask as $m) {
   echo $m;
}

edited Mar 11, 2012 at 12:55

answered Mar 11, 2012 at 4:58

Michael Berkowski

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3 Comments

Michael Pasqualone Over a year ago

Thanks, but I'm still confused where the duplicate data is coming from. Does $array within each loop somehow still contain the whole XML structure? and print_r is hiding it or something?

Michael Pasqualone Over a year ago

My problem with having the xpath query first is, that I want to perform multiple xpath queries on each array node to match not only mask, but also on keys: id, name and email.

Michael Berkowski Over a year ago

@MichaelP There isn't duplicate data - It's just that because your xpath query starts with ` //, each time you execute it in the loop you get the exact same nodelist returned. So the value $mask[0]` is the same on every loop iteration.

salathe · Accepted Answer · 2012-03-11 13:03:39Z

2

Starting the location path in xpath() with / makes it "absolute", whereas you want to query "relative" to the $array element. For your example, just take out the //.

foreach ($load_test as $array)
{
    $mask = $array->xpath('string[@key="mask"]');

    print 'Mask: ' . $mask[0] . '<br />';
}

See also http://www.sitepoint.com/forums/showthread.php?723058-php-xml-loop&p=4778177&viewfull=1#post4778177

answered Mar 11, 2012 at 13:03

salathe

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Comments

Michael Pasqualone · Accepted Answer · 2012-03-11 05:50:32Z

Until I can better understand what's going on, the following outputs what I am after; allowing me to match on the key attributes.

$xml_test = '<array key="results">
    <array key="123">
        <string key="mask">1234</string>
        <string key="name">mick</string>
    </array>
    <array key="987">
        <string key="mask">5678</string>
        <string key="name">bob</string>
    </array>
</array>';

$simplexml= new SimpleXMLElement($xml_test);

$test = $simplexml->xpath('//array/array');

$loop = 0;
foreach ($test as $result)
{
    $mask = $result->xpath('//string[@key="mask"]');
    $name = $result->xpath('//string[@key="name"]');

    echo "Mask: " . $mask[$loop] . '<br />';
    echo "Name: " . $name[$loop];
    $loop++;
}

Returns:

Mask: 1234
Name: mick

Mask: 5678
Name: bob

Not sure how clean the above is, but it ultimately does what I need it to do.

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