Somewhat similar to http://stackoverflow.com/questions/2002970/export-a-variable-from-php-to-shell, but my problem is different.

I am forced to work with a program that gets an important location variable from an Environment Variable (Linux), rather than a config or, better, a command line option.

I have to call this program from within PHP, and currently am doing it like so:

shell_exec('/path/to/program option1 option2'); 

I need to be able to set/override the environment variable that program will be looking for. As an example, this does not work:

shell_exec('VAR1=foo /path/to/program option1 option2'); 

nor does:

shell_exec('VAR1=foo; export foo; /path/to/program option1 option2'); 

for good measure.

Both of the above command lines work "as expected" from the shell.

Is it possible to override environment variables for programs called via exec, shell_exec, etc?