PHP Notice: Array to string conversion + Linux

Question

PHP simplexml_load_string command is throwing error on very very large string on Linux server. However on PC with WAMP server it works.

code:

set_error_handler(array($this, 'handleXmlErrors'));
$this->_objSimpleXml = simplexml_load_string($data, 'SimpleXMLElement', LIBXML_NOCDATA | LIBXML_PARSEHUGE); 
restore_error_handler()

;

error is: “PHP Notice: Array to string conversion in ...”

versions:

                         PHP             libxml
    Linux (Red Hat)      5.4.16          2.9.1 
    PC (WAMMP)           5.4.38          2.7.8

Is this likely an issue with Linux, versions of software or something else?

thanks