This is a known cosmetic issue in var_dump().  If you actually iterate through the 
object it works fine.

I'm not concerned about var_dump(). I think more of json_encode() which has the same issues. I use json_encode/json_decode to transform a SimpleXml object to an array.

print_r(json_decode(json_encode($xml), true)));

have same problem, it's not var_dump error, because print_r has same trouble

code:
$xmlObj = simplexml_load_string($xml_string);
print_r ($xmlObj);

I have the same problem, i have PHP 5.5.10 x86_64, linux 3.13.6

As circus2 at freenet dot de points out, this is not merely a var_dump() issue.

Here's a repro from the linked issue (Bug #66084); note the only difference in input is a single space in the XML:

echo json_encode(simplexml_load_string('<a><b/><c><x/></c></a>')), PHP_EOL;
echo json_encode(simplexml_load_string('<a><b/><c> <x/></c></a>'));

This is only a bug when printing the values. SimpleXML IS parsing the attributes and you can reference them:

$string = '
<xml>
	<value type="string" key="name"></value>
	<value type="string" key="name">myValue</value>
</xml>
';

$xml = simplexml_load_string($string);

foreach( $xml as $element ) {
	echo $element."\n";
	foreach( $element->attributes() as $key=>$value) {
		echo "\t".$key."=>".$value."\n";
	}
}

will result in


	type=>string
	key=>name
myValue
	type=>string
	key=>name

The attributes (their keys and values) are there. They just don't print out properly when using var_dump, print_r, echo, etc... Just use the ->attributes() method to reference them. However, if this printing/display bug is something to do with SimpleXML it should definitely be fixed. Because this is very misleading to not see the attributes when doing a var_dump.