PHP HTML DomDocument getElementById problems

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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 ca

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我在风中等你

2020-11-27 07:47
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']"));
```
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春和景丽

2020-11-27 08:08
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:
1. 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.
2. Use XPath if you don't feel like validing: $x = new DOMXPath($dom); $el = $x->query("//*[@id='bid']")->item(0);
3. 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.
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