Trying to remove XML element with PHP using an HTML form. Element not removed

Question

I have an HTML form that calls a PHP document post_remove.php on submission. post_remove.php checks a hidden input value value="pst_09-12-2014_07:20:11pm"> to find an id attribute that matches in data.xml to be removed. id="pst_01-01-2014_05:00:00pm" I am using a form value to compare. $check = $_POST["validate"] ;

I have tried many alternatives such as loops with no luck and also felt they were unneccesary since I only want one element removed. I can't seem to get any elements to be removed.

My HTML form blog_home.html:

<div class="blog_wrap">
   <p>01-01-2014</p>
   <p>05:00:00pm</p>
   <h1>My first Blog</h1>
   <p>Welcome to my Blog!</p>

   <form method="post" action="post_remove.html">
      <input type="hidden" name="validate" value="pst_01-01-2014_05:00:00pm">
      <input type="submit" name="closer">
   </form>
</div>

My XML document data.xml:

<?xml version="1.0" encoding="UTF-8"?>
<blog>
<posting id="pst_01-01-2014_05:00:00pm">
   <date>01-01-2014</date>
   <time>05:00:00pm</time>
   <title>My first Blog</title>
   <content>Welcome to my Blog!</content>
</posting>
<posting id="pst_02-02-2014_06:00:00pm">
   <date>02-02-2014</date>
   <time>06:00:00pm</time>
   <title>My Second Blog</title>
   <content>Welcome to my Blog!</content>
</posting>
</blog>

My PHP document post_remove.php:

<?php
if ( isset( $_POST["closer"] ) )
   {
   $check = $_POST["validate"] ;

   $doc = new DOMDocument() ;
   $doc -> load( "data.xml" ) ;

   $posting = $doc -> getElementById( $check ) ;// Suspected fault.

   $doc -> removeChild( $posting ) ;
   $doc -> save( "data.xml" ) ;
   header( "Location: blog_home.html" ) ;
   }
?>

Sidenote: Your action shows `action="post_remove.html"` but your file is `post_remove.php` - it should be `action="post_remove.php"` — Funk Forty Niner, Sep 13 '14 at 04:03
why do you have a header redirect above the removing of the nodes? you remove the nodes, then after its complete, redirect — Kevin, Sep 13 '14 at 04:13
@Ghost I wondered about that. Thanks for the tip. I really felt it should be last in the first place. — Xavier, Sep 13 '14 at 04:14
@Xavier actually i was trying to answer your question, and also failed, but i found out that you cannot use `getElementById` on XMLs, here a [reading](http://stackoverflow.com/questions/3405117/simplify-php-dom-xml-parsing-how/3405651#3405651) about it if why it is, the only solution presented was thru XPath — Kevin, Sep 13 '14 at 04:24
@Ghost I do not want to use other Parsers. How about finding a match with `childNode[x]` using a `for()` loop? — Xavier, Sep 13 '14 at 04:28
@Xavier well whatever works for you, xpath is actually nice though and that i will recommend, but if you want to loop it then go for it :) — Kevin, Sep 13 '14 at 04:30
@Ghost Well I tried the loop route and could not get a resulting removed element. I also tried the `foreach()` loop. — Xavier, Sep 13 '14 at 04:32
@Xavier derp's answer is the most feasible +1, i suggest take that route — Kevin, Sep 13 '14 at 04:36

score 2 · Accepted Answer · answered Sep 13 '14 at 04:30

Just because the attribute name is id does not mean the DOM assumes the attribute to be of type id. Per the PHP manual entry on getElementById:

For this function to work, you will need either to set some ID attributes with DOMElement::setIdAttribute or a DTD which defines an attribute to be of type ID. In the later case, you will need to validate your document with DOMDocument::validate or DOMDocument::$validateOnParse before using this function.

If you don't feel like creating a DTD to specify that @id is indeed an ID you can use an XPath expression to easily grab the elements where the attribute matches.

Like so:

$doc = new DOMDocument() ;
$doc -> load( "data.xml" ) ;

$xpath = new DOMXPath($doc);

$postings = $xpath->query("/blog/posting[@id='$check']");
foreach ($postings as $posting) {
    $posting->parentNode->removeChild($posting);
}

$doc -> save( "data.xml" ) ;

Note: You also don't remove the child from the DOMDocument itself, but instead from the child's parent node.

Trying to remove XML element with PHP using an HTML form. Element not removed

1 Answers1

Like so: