PHP HTML DOMDocument getElementById problems
A little new to PHP parsing here, but I can't seem to get PHP's DOMDocument to return what is clearly an identifiable node. The HTML loaded will come from the 'net so can't necessarily guarantee XML compliance, but I try the following:
<?php
header("Content-Type: text/plain");
$html = '<html><body>Hello <b id="bid">World</b>.</body></html>';
$dom = new DOMDocument;
$dom->preserveWhiteSpace = false;
$dom->validateOnParse = true;
/*** load the html into the object ***/
$dom->loadHTML($html);
var_dump($dom);
$belement = $dom->getElementById("bid");
var_dump($belement);
?>
Though I receive no error, I only receive the following as output:
object(DOMDocument)#1 (0) {
}
NULL
Should I not be able to look up the <b> tag as it does indeed have an id?
Solution 1:
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
validateOnParseto 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.
Solution 2:
Well, you should check if $dom->loadHTML($html); returns true (success) and I would try
var_dump($belement->nodeValue);
for output to get a clue what might be wrong.
EDIT: http://www.php-editors.com/php_manual/function.domdocument-get-element-by-id.html - it seems that DOMDocument uses XPath internally.
Example:
$xpath = xpath_new_context($dom);
var_dump(xpath_eval_expression($xpath, "//*[@ID = 'YOURIDGOESHERE']"));