Fatal error: Cannot redeclare encrypt() (previously declared in
Make sure you didn't declare the function in the same name "encrypt" in any of the included file such as 'lib/nusoap.php', 'lib/nusoapmime.php' or in your current file 'tax_calculation.php'.
If you are using any IDE like net-beans or eclipse, just import the project in the IDE and search for the function name. You can easily find the total occurrence. Then rename the function name and check.