Can't read large XML file from PHP

 Error will come 

Warning: simplexml_load_string(): Entity: line 1: parser error : internal error: Huge input lookup

For this we have to use

$xml =  @simplexml_load_string($data, 'SimpleXmlElement', LIBXML_PARSEHUGE );

or 

$doc3->load($masternumber.'.xml', LIBXML_PARSEHUGE);