Scenario: My Cpanel server is installed with multiple php version and All of a sudden all my sites thrown 500 internal server error.
Troubleshooting: The logs was showing the following message
Caused by SystemException in API_Linux.cpp:444: execve() for program “/usr/bin/php” failed: Permission denied
Resolution: I checked and I could see that the permission of “/usr/bin/php” was 000. I changed it to 755 and it fixed the issue
chmod 755 /usr/bin/php