Export to excel error in PHP reports

I export reports as excel using PHP & MySql. I can export and open the file from my localhost using my source code, but unable to do in the server. When I try to export it shows
"
Warning: tempnam() [function.tempnam]: open_basedir restriction in effect. File() is not within the allowed path(s): (/home:/tmp:/usr) in /home/xx/xx.inc.php on line 205."
I googled through, but I'm unable get the solution.

$this->_tmpfilename=tempnam("/tmp", "excelreport");

$fh=fopen($this->_tmpfilename, "w+b");

This is the code that used. What's wrong.