xpath_eval

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marius kreis (email to mariuskreis . de)
08-Jul-2005 10:26


If the namespace is subject to change you can write even more portable code if you extend brandon dot whitehead at orst dot edu's solution like this:



$doc = domxml_open_mem($xml);



$xpath = $doc->xpath_new_context();

$namespace = $xpath->xpath_eval('namespace-uri(//*)')->value; // returns the namespace uri



xpath_register_ns($xpath, "pre", $namespace); // sets the prefix "pre" for the namespace

$obj = $xpath->xpath_eval('//pre:Offer'); // finds all Offer tags



$nodeset = $obj->nodeset;



print_r($nodeset);



This code will determine the namespace of the root element and set a prefix for XPath queries. Thus it doesn't matter if the namespace is changing in your XML (like some webservices do...)

patrikG at home dot net
17-Mar-2004 12:42


Just an example of how to grab XML attributes with xpath - which took me a while to figure out. I'm filtering the returned object function node_content() which is a somewhat quick'n dirty solution, but I don't always need XML's child-parent relationships.



<?php

$xml='<MY_SERVICE>

    <MERCHANDISE>

        <SERVICE TYPE="books">

            <NAME>Ulysses</NAME>

        </SERVICE>

        <SERVICE TYPE="books">

            <NAME>The Poisonwood Bible</NAME>

        </SERVICE>

        <SERVICE TYPE="cars">

            <NAME>Van</NAME>

        </SERVICE>

        <SERVICE TYPE="vehicle sans wheels">

            <NAME>UFO</NAME>

        </SERVICE>

    </MERCHANDISE>

</MY_SERVICE>';



echo "<h4>XML</h4><xmp>";print_r(parse_XML($xml));echo"</xmp>";



function node_content($node,$attribute="content"){

    foreach($node->nodeset as $content){

        $return[]    =    $content->{$attribute};

    }

    return $return;

}



function parse_XML($xml){

    //needs PHP's xPath extension installed

    $dom    =domxml_open_mem($xml); 

    $calcX = &$dom->xpath_new_context();

$xml_parsed["merchandise"]=node_content(

        $calcX->xpath_eval("//MERCHANDISE/SERVICE/NAME/text()")

        );

$xml_parsed["service"]=node_content(

        $calcX->xpath_eval("//MERCHANDISE/SERVICE/attribute::TYPE",$calcX)

        ,"value");

    return $xml_parsed;

}

?>



The code above returns:



XML

Array

(

    [merchandise] => Array

        (

            [0] => Ulysses



            [1] => The Poisonwood Bible

            [2] => Van

            [3] => UFO

        )



    [service] => Array

        (

            [0] => books

            [1] => books

            [2] => cars

            [3] => vehicle sans wheels

        )



)

brandon dot whitehead at orst dot edu
07-Sep-2003 04:52


In order to use the default namespace you must understand 

how namespace prefixes work.  Prefixes are simply convenient mappies to the namespace URI.



For example, if you set the namespace: 



xmlns:xm="http://www.someurl.org"



and you have the following document fragment:



<rootnode><xm:childnode>Text</xm:childnode></rootnode>   



this is essentially equivalent to:



<rootnode>

   <http://www.someurl.org:childnode>

      Text

   </http://www.someurl.org:childnode>

</rootnode>   



because the namespace URI is what matters, not the namespace prefix.



Unfortuantly, if you have a default namespace:



xmlns="http://www.anotherurl.org" 



then all elements without a prefix belong to that namespace, and yet, it appears that PHP, and the underlying LIBXML2 don't let you register a default namespace with 



"xpath_register_ns(context, prefix, uri)" 



i.e. by leaving the prefix = "".  Therefore, to get around the problem, simply give the default prefix a simple name, such as "pre".  



For example, if you have a default namespace declaration such as the following document:



<?xml version="1.0" encoding="UTF-8"?>

<rootname xmlns="http://www.some.org" xml:lang="en-US">

   <childnode>Some text</childnode>

</rootname>



And you want to evaluate the xpath expression: 



"/rootname/childnode"



then you need to register the default namespace in PHP like this:



xpath_register_ns(context, "pre", "http://www.some.org");



and then use the following xpath expression: 



"/pre:rootname/pre:childnode"



As you can see this is a lot prettier and more intuititive than using the local-name() function.  In addition, it makes your code more portable, because you are guaranteed to always be working on nodes that belong to your explicitly stated namespace, uniquely identified by your URI.

fabiostt[X_AT_X]libero[X_DOT_X].it
07-Sep-2003 01:05


Querying documents closed inside a namespace can be tricky



http://bugs.php.net/bug.php?id=11903

tuxo at gmx dot net
22-May-2003 02:47


PHP Version: 4.3.1



I tried out how to get a part of a xml document with the xpath functions in domxml.

Try the following solution:



<?php

// get dom object

$xmldoc = domxml_open_mem($xml);



// init xpath

$xpath = xpath_new_context($xmldoc);

$xpresult = xpath_eval($xpath, "/root/info");



// dump all nodes directly in plain text

foreach ($xpresult->nodeset as $node)

{

    $newxml .= $node->dump_node($node);

}

?>



If you wanna get a new dom object of the result just add



$newxmldoc = domxml_open_mem($newxml);

tk dot lists at fastmail dot fm
20-Jan-2003 09:46


You can indeed use the result object of xpath_eval(). You just have to be careful to pass the result by reference! (note the ampersand's position).



$objXP = xpath_new_context($objDom)

$objTest = &xpath_eval($objXP,"//lalala");

$objTest->nodeset[0]->set_attribute("test","test data");

echo htlentities($objDom->dump_mem());



just be careful that is you pass around values from $objTest then they also need to be passed by reference.

chregu at php dot net
29-Nov-2002 06:32


If you want to apply an XPath-Expression to a particular node:





$ctx->xpath_eval("xpath",$node);

arthur at ischium dot net
09-Nov-2002 07:54


If you want to get the XPath for a particular node:



function getXPath($node) {

    /* node id is held in a property named '1', this is

    illegal in php so we use a workaround */

    $one = '1';

    $xpath = '';

    while ($parent = $node->parent_node()) {

        $siblings = $parent->child_nodes();

        $index = 1;

        foreach ($siblings as $sibling) {

            if ($sibling->type != XML_ELEMENT_NODE || $sibling->tagname != $node->tagname) continue;

            if ($sibling->$one == $node->$one) {

                $xpath = '/' . $node->tagname . '[' . $index . ']' . $xpath;

                break;

                   } 

            $index++;

            } 

        $node = $parent;

        } 

    return $xpath;

    }

bate at php dot net
04-Oct-2002 07:58


<?

$xml = xmldocfile('file.xml');

$xpath = $xml->xpath_new_context();



/**

* object access

*/

$ret = $xpath->xpath_eval('//tag');



/**

* function access

*/

$ret2 = xpath_eval($xpath, '//tag');



print_r($ret);

print_r($ret2);

?>

sbarnum@pointsystems com
21-Mar-2002 10:33


This function has come in handy for recursively viewing the results of xpath searches.  It iterates through a node and converts it to a big associative array:



/**

* Recursive function to convert xml root node to big assoc array

*/

function xmlnode2array($node) {

    if ($node->type==XML_ELEMENT_NODE) {

        if ($attrArray = $node->attributes()) {

            // parse attributes //

            foreach($attrArray AS $attr) {

                $out['ATTRIBUTE'][$attr->name] = $attr->value;

            }

        }

        if ($childArray = $node->children()) {

            // add child nodes //

            foreach($childArray AS $child) {

                if ($child->type==XML_ELEMENT_NODE) {

                    $out[$child->tagname][] = xmlnode2array($child);

                } else {

                    if ($content = xmlnode2array($child))

                        $out['CONTENT'] = $content;

                }

            }

        }



    } else { 

        // this is a CONTENT NODE //

        $out = trim($node->content);

        if (!$out) return false;

    }

    return $out;

}

ziw at ifirst dot ru
22-Oct-2001 08:34


it seems that namespaces are not yet (PHP 4.06) implemented - xpath_eval($cnx,"/ns:tag") does work on w2k and does NOT on linux

sofnology at xtra dot co dot nz
26-Aug-2001 09:45


I hope this little example helps someone out. If the XML data doesn't come thru in the post feel free to contact me via email.





<?


    $p = xslt_create();





    $o += 0;


    $s =  '';


    $s .= "<query type='create'>";


    $s .=     "<resourceClass id='12345678901234567890' displayName='DAISY'>";


    $s .=         "<group family='global' id='kind'>";


    $s .=             "<node id='NODE_A' displayName='Red Ferrari' description='Red always goes faster'/>";


    $s .=         "</group>";


    $s .=     "</resourceClass>";


    $s .=     "<resourceClass id='12345678901234567890' displayName='BETTY'>";


    $s .=         "<group family='global' id='kind'>";


    $s .=             "<node id='NODE_B' displayName='Blue Porsche' description='But Porsches are a drivers car'/>";


    $s .=         "</group>";


    $s .=     "</resourceClass>";


    $s .= "</query>";





    $dom=xmldoc($s);


    $ctx=xpath_new_context($dom);





    $query_xo = xpath_eval($ctx,"count(/query/resourceClass)");


    $num_rc = $query_xo->value;


    echo("<BR>There are $num_rc classes in this list");





    for($x=1; $x <= $num_rc; $x++){


        $query_xo = xpath_eval($ctx,"/query/resourceClass[position()=$x]");


        $query_ns = $query_xo->nodeset;


        $resourceClass_dn = $query_ns[0];





//        echo("<PRE>");


//        print_r( $query_xo );


//        echo("<PRE><HR>");


//        print_r( $query_ns );


//        echo("<PRE><HR>");


//        print_r( $rc_dn );


        echo("<BR>[id::".$resourceClass_dn->get_attribute('id')."][displayName::".$resourceClass_dn->get_attribute('displayName')."]");





    }


?>

mfkahn2_NOSPAM at yahoo dot com
25-Jun-2001 05:35


$ctx = xpath_new_context($doc);


$xpath_nodes = xpath_eval($ctx, "//some_element");





$xpath_nodes->nodeset[i]->set_content($string) allows you to set the node content.  Try it and then do a $doc->dumpmem, you'll see the nodes in the original document are indeed updated properly.





I've used this feature lots.  It does work.

newsforsam at bigfoot dot de
24-May-2001 11:46


xpath_eval() returns only a copy of your document. So you cant for example change the $foo->nodeset[id]->content's of the resulting matches. If you want to, you have to do it yourself by going recursive through your doc, which makes xpath_eval at least useless except for checking if you have to ;).

28-Mar-2001 10:12


actually the description at the top should read:


 object xpath_eval(object context, string xpath);

pking at hoovers dot com
07-Mar-2001 09:22


This is a very (very) minor point, but there is a comma missing in the function definition for xpath_eval.  This being my first experience with xpath, I thought "object xpath context" was refering to a single parameter produced by a previous call to xpath_new_context().  Then I couldn't see where you would add the query (which is actually the context parameter)





So the proper definition should be


array xpath_eval (object xpath, context)





Additionally an example would be nice.  I found one from a post to phpbuilder.com:


-------------------------------


http://www.phpbuilder.com/annotate/message.php3?id=1002772


-------------------------------


Message # 1002772: 


Date: 01/02/01 06:40 


By: Luis Argerich 


Subject: new DOM features im 4.0.4 





Just wanted to add that PHP 4.0.4 has improved DOM support including Xpath and 


Xpointer support: 





Try this: 





$xml='SOME XML ....'; 


$doc=xmldoc($xml); 


$ctx=xpath_new_context($doc); 


$foo=xpath_eval($ctx,"//title"); 


print_r($foo); 





It returns an object that contains a property called Nodeset with an array of DomNodes with the result of the Xpath expression. print_r($foo) to see the full structure. 





4.0.4 has also added Xpointer support, so with Xpath and Xpointer support we can really do a lot of things from PHP to XML files. 





Luis.

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