Simplexmlelement php class

Fatal error: Cannot instantiate non-existent class: simplexmlelement in /usr/local/psa/home/vhosts/brendanmeade.co.nz/httpdocs/newwave/data_retrieve.php on line 5

Hi just got this message.
I am presuming that simplexmlelement (althought it is simpleXMLelement)
is a class that only php5 supports?

advice?

thanks in advance