How do I allow www-data user to execute bash script with nginx

The result of shell_exec() is returned as string. To display it in your browser, simply add echo.

<?php    chdir('/path/to/my/files/');    echo shell_exec('./script_test.sh');  // ATTEMPT RUN SCRIPT    echo shell_exec('/path/to/my/files/script_test.sh');  // ATTEMPT RUN SCRIPT    echo 'test 123';  // SIMPLE ECHO IN THE PHP PAGE?>

See the Return Values in the manual:

The output from the executed command or NULL if an error occurred or the command produces no output.

Can you try to use passthru instead of shell_exec, and see the output anything?

Also try this, and see if it shows on the log file:

if(file_exists('/path/to/my/files/script_test.sh')) { die('File not found!'); }shell_exec("nohup /path/to/my/files/script_test.sh > /path/to/my/files/output.log &");

Also, are you running PHP with the www-data user (check your fpm pool)?Do you have any error on /var/log/syslog or /var/log/auth.log ?Have you restarted the server after changing the sudo permissions?

What does su - www-data -c "whoami" and su - www-data -s /bin/bash -c "whoami" outputs?

Does su - www-data -s /bin/bash -c "/path/to/my/files/script_test.sh" output something?