系统输出未在Web浏览器中显示php

Question

I have a command I have tested in the terminal and it works fine, but when I call the command in my script to display the output on the browser it doesn't seem to work. My command takes time for it to display the output in the terminal would this be a contribution why its not displaying on the browser.

set_time_limit (0); 
echo '<pre>';
$output=array();
$last_line = system('cat /home/me/dev/test/working/test_string.txt | java -jar /home/simon/logstash/build/logstash-1.1.10.dev-monolithic.jar agent -f /home/me/dev/test/working/my_itch_con.config',$output);
echo '</pre>';
echo "Complete";
print_r($output);
echo "<br>"; 

Answer 1

Confirm whether you disable system function in php.ini in disable_function block

When set error_reporting(E_ALL) to display all error