PHP DomXPath - "object value omitted" even if new DomDocument is not empty? - domxpath

Question

I have a xml file like this...
XML File
<?xml version="1.0" encoding="UTF-8"?>
<database xmlns="tt:foo" xmlns:h4a="https://www.myexample.com/foo.xsd" >
<tables>
<table name="my_first_table_name">
<column name="column_name_1" />
</table>
</tables>
</database>
I 'm trying to use DOMXPath for a future xml merging.
PHP Code
$doc_ref = new \DOMDocument();
$doc_ref->load( $array_xml_paths[0] );
$xpath_ref = new \DOMXPath($doc_ref);
error_log_array( $xpath_ref );
foreach ($xpath_ref->evaluate('//table[#name]') as $table) {
$table_name = $table->getAttribute('name');
error_log( $table_name );
}
output
[08-Mar-2018 14:21:47 UTC] DOMXPath Object
(
[document] => (object value omitted)
)
The DOMDocument is correclty loaded, but something more seems to be necessary for DOMXPath to work it but I don't know.

Answer 1

First of all...
[document] => (object value omitted) DOES NOT MEAN the DOMXPath instance is empty !
I found the solution. It was in this comment.
I had to register the xml namespace to use evaluate().
Solution
$doc_ref = new \DOMDocument();
$doc_ref->load( $array_xml_paths[0] );
$xpath_ref = new \DOMXPath( $doc_ref );
$ns = $doc_ref->documentElement->namespaceURI;
if($ns) {
$xpath_ref->registerNamespace("ns", $ns);
foreach ($xpath_ref->evaluate('//ns:table[#name]') as $table) {
$table_name = $table->getAttribute('name');
error_log( $table_name );
}
}else {
foreach ($xpath_ref->evaluate('//table[#name]') as $table) {
$table_name = $table->getAttribute('name');
error_log( $table_name );
}
}