How to set Exact XML element name in DomDocument with PHP

I have a form which on POST creates an XML based on the values in the form. I am using DOM DOCUMENT to create XML. I am giving exact element names when creating xml but when it is created the element names are in lowercase which my API is not accepting. for eg.

I am giving this as an input <LSP_Name>JaVAS</LSP_Name> and when it is created it forms like this <lsp_name>JaVAS</lsp_name>

I tried $xml->formatOutput=true; but had no luck.

Any one who had faced this similar issue ?

DOCUMENT CREATION

$xml = new DOMDocument('1.0', 'utf-8');

        $xml->formatOutput=true;
        $root = $xml->createElement("NewDataSet");
        $xml->appendChild($root);

        $LSP_Code   = $xml->createElement("LSP_Code");
        $LSP_CodeText = $xml->createTextNode(LSP_CODE);
        $LSP_Code->appendChild($LSP_CodeText);

        $docket = $xml->createElement("Docket");
        $root->appendChild($docket);
        $docket->appendChild($LSP_Code);

TIA