Crystal Report by using CRExport via PHP

Crystal Report by using CRExport via PHP

I'm trying to generate a crystal report via a php script. I was able to
successfully use crexport to generate a pdf report. However when I try to
execute the script via php's exec command I get this error.
c:\inetpub\wwwroot\mamobile\crexport -F
c:\inetpub\wwwroot\mamobile\reports\customer.rpt -O
c:\inetpub\wwwroot\mamobile\output\test.pdf -E pdf -S testdb
Crystal Reports Exporter Command Line Utility. Version 2.1.11.1103
Copyright(c) 2011 Rainforest Software Solution http://www.rainforestnet.com
Misc Error: Load report failed.
Type "crexport -?" for help
It works fine via the command prompt.