I created a simple php script:

<?php
  echo 'Hi';
  error_log( 'Test!' );
  system( 'date' );
  system( 'ls' );
  echo 'There!';
?>

I see “HiThere!” on webpage and “*58 FastCGI sent in stderr: “PHP message: Test!” in error_log.
Nothing from system() calls appears on webpage nor error_log. I also tried various other simple commands in system() and none of them produce any output. What is wrong here and how to fix this?