PHP HTML Domdocument Getelementbyid Problems

PHP HTML DOMDocument getElementById problems

The Manual explains why:

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.

By all means, go for valid HTML & provide a DTD.

Quick fixes:

Call $dom->validate(); and put up with the errors (or fix them), afterwards you can use $dom->getElementById(), regardless of the errors for some reason.
Use XPath if you don't feel like validing: $x = new DOMXPath($dom); $el = $x->query("//*[@id='bid']")->item(0);
Come to think of it: if you just set validateOnParse to true before loading the HTML, if would also work ;P

$dom = new DOMDocument();
$html ='<html>
<body>Hello <b id="bid">World</b>.</body>
</html>';
$dom->validateOnParse = true; //<!-- this first
$dom->loadHTML($html);        //'cause 'load' == 'parse

$dom->preserveWhiteSpace = false;

$belement = $dom->getElementById("bid");
echo $belement->nodeValue;

Outputs 'World' here.

Alternatives to PHP getElementById() of DOMDocument?

Got it, don't know how it's invalid-document-proof:

$xpath = new \DOMXpath($document);
$nodes = $xpath->query('//img[@id="banner"]');

// Return content if we don't have exactly one image with id="banner"
if(1 !== $nodes->length) return $content;

// DOMNode of the banner
$banner = $nodes->item(0);

// Set the new src attribute and save the content
$banner->setAttribute('src', 'http://mysite.come/img/myimage.png');
$banner->ownerDocument->saveXML($banner);

return $document->saveXML();

DOM getElementbyId doesn't work properly

As noted in comments on the doc page, you must declare a doctype for getElementById to perform as expected

t =<<<D
<!DOCTYPE html>
<form id="frm-send" method="post"   action="index.php"   >

...code continues ...

Per the documentation, a DTD must be specified for getElementById to understand which attribute of an element is used as the unique identifier. Declaring a doctype accomplishes this. You may also explicitly set this (without giving a DTD) by using setIdAttribute,

Documentation

http://www.php.net/manual/en/domdocument.getelementbyid.php
http://www.php.net/manual/en/domelement.setidattribute.php

DOMDocument getelementbyid conflict?

You can use a DOMXPath query instead of getElementById() to dodge the name attribute and target only the element with an id attribute of "favela":

$xpath = new DOMXPath($doc);
$favelaElement = $xpath->query('//*[@id="favela"]')->item(0);

print_r($favelaElement->nodeValue);

Output:

A shantytown or slum, especially in Brazil.

php DOMDocument- getElementById- nodeValue sripping html

This is proper behavior - your tag is being converted to a string, and strings in XML can't contain angle brackets (only tags can). Try converting the HTML into a DOMNode and appending it instead:

$node = $mydoc->createElement("b");
$node->nodeValue = "test";
$mydoc->getElementById("whatever")->appendChild($node);

Update with working example:

$html = '<html>
    <body id="myBody">
        <b id="myBTag">my old element</b>
    </body>
</html>';

$mydoc = new DOMDocument("1.0", "utf-8");
$mydoc->loadXML($html);

// need to do this to get getElementById() to work
$all_tags = $mydoc->documentElement->getElementsByTagName("*");
foreach ($all_tags as $element) {
    $element->setIdAttribute("id", true);
}

$current_b_tag = $mydoc->getElementById("myBTag");
$new_b_tag = $mydoc->createElement("b");
$new_b_tag->nodeValue = "my new element";
$result = $mydoc->getElementById("myBody");
$result->replaceChild($new_b_tag, $current_b_tag);

echo $mydoc->saveXML($mydoc->documentElement);

DOMDocument::getElementById returns NULL

I think The Manual explains why this may happen

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.

Potential fixes:

Call $dom->validate();, afterwards you can use $dom->getElementById(), regardless of the errors for some reason.
Use XPath if you don't feel like validating:
$x = new DOMXPath($dom);
$el = $x->query("//*[@id='title']")->item(0); //Look for id=title

Example of using a custom DTD:

$dtd = '<!ELEMENT note (to,from,heading,body)>
        <!ELEMENT to (#PCDATA)>
        <!ELEMENT from (#PCDATA)>
        <!ELEMENT heading (#PCDATA)>
        <!ELEMENT body (#PCDATA)>';

$systemId = 'data://text/plain;base64,'.base64_encode($dtd);

$creator = new DOMImplementation;
$doctype = $creator->createDocumentType($root, null, $systemId); //Based on your DTD from above

Document::getElementById('content') doesn't work, but the element is there

I found this:

Please note that if your HTML does not contain a doctype declaration,
then getElementById will always return null.

By looking for tagname and then the ID of that tag name, it will return the id.

Source

PHP HTML Domdocument Getelementbyid Problems