Q: PHP DOMDocument how to get that content of this tag? I am using domDocument hoping to parse this little html code.  I am looking for a specific span tag with a specific id.
<span id="CPHCenter_lblOperandName">Hello world</span>

My code:  
$dom = new domDocument;
@$dom->loadHTML($html); // the @ is to silence errors and misconfigures of HTML
$dom->preserveWhiteSpace = false;
$nodes = $dom->getElementsByTagName('//span[@id="CPHCenter_lblOperandName"');

foreach($nodes as $node){
    echo $node->nodeValue;
}

But For some reason I think something is wrong with either the code or the html (how can I tell?):  


*

*When I count nodes with echo count($nodes); the result is always 1

*I get nothing outputted in the nodes loop

*How can I learn the syntax of these complex queries?

*What did I do wrong?


A: You can use simple getElementById:
$dom->getElementById('CPHCenter_lblOperandName')->nodeValue

or in selector way:
$selector = new DOMXPath($dom);

$list = $selector->query('/html/body//span[@id="CPHCenter_lblOperandName"]');

echo($list->item(0)->nodeValue);

//or 
foreach($list as $span) { 
    $text = $span->nodeValue;
}


A: Your four part question gets an answer in three parts:


*

*getElementsByTagName does not take an XPath expression, you need to give it a tag name;

*Nothing is output because no tag would ever match the tagname you provided (see #1);

*It looks like what you want is XPath, which means you need to create an XPath object - see the PHP docs for more;


Also, a better method of controlling the libxml errors is to use libxml_use_internal_errors(true) (rather than the '@' operator, which will also hide other, more legitimate errors). That would leave you with code that looks something like this:
<?php    
libxml_use_internal_errors(true);
$dom = new DOMDocument();
$dom->loadHTML($html);
$xpath = new DOMXPath($dom);
foreach($xpath->query("//span[@id='CPHCenter_lblOperandName']") as $node) {
    echo $node->textContent;
}

