如果xml元素名称相同，如何设置xml属性值更改

Question

I have the following XML file:

<root>
  <SignUp user_id = 'joseph' image = 'myByk.jpg' />
  <SignUp user_id = 'jack' image = 'myCar.jpg' />  
  <SignUp user_id = 'lamp' image = 'myhome.jpg' />
</root>

Within this file I want to get the SignUp element with the user_id " jack ", and change its image attribute.

I have tried the following PHP code:

<?php
  $dom = new DomDocument();
  $dom->load('data_out.xml');
  $xp = new DomXPath($dom);
  $res = $xp->query("//*[@user_id = 'jack']");
  $xp->SignUp->attributes()->image = "my School.jpg";
  $dom->save('data_out.xml');
?>

However, it doesn't seem to be working...

Answer 1

Since in the query you are going by attribute you can have multiple result elements so it is wrapped in a list of some sort ( dom node list ).

Here is what I am thinking (untested):

<?php
    $dom = new DomDocument();
    $dom->load('data_out.xml');
    $xp = new DomXPath($dom);
    $res = $xp->query("//*[@user_id = 'jack']");
    $res->item(0)->setAttribute("image", "my School.jpg");
    $dom->save('data_out.xml');
?>

---

Similar code successfully tested in a sandbox :

$dom = new DomDocument();
$dom->loadXML(
    "<root>
        <SignUp user_id = 'joseph' image = 'myByk.jpg' />
        <SignUp user_id = 'jack' image = 'myCar.jpg' />  
        <SignUp user_id = 'lamp' image = 'myhome.jpg' />
    </root>"
);
$xp = new DomXPath($dom);
$res = $xp->query("//*[@user_id = 'jack']");
$res->item(0)->setAttribute("image", "my School.jpg");
$ret =  $dom->saveXML();
echo $ret;

returns

<?xml version="1.0"?>
<root>
    <SignUp user_id="joseph" image="myByk.jpg"/>
    <SignUp user_id="jack" image="my School.jpg"/>  
    <SignUp user_id="lamp" image="myhome.jpg"/>
</root>

Answer 2

Then perhaps the op should consider using SimpleXML:

if ($root = simplexml_load_file('xml.xml') ) 
{
    //access attributes like an array:
    echo $root->SignUp[0]["user_id"] . "\n";  

    $target_elements = $root->xpath("//*[@user_id = 'jack']");
    $target_elements[0]["image"] = "mySchool.jpg";
    $root->asXML('datat_out.xml');

}

Note that to change an attribute, you don't have to use the cumbersome:

$target_attr = "image";
$target_elements[0]->attributes()->$target_attr = "hello";