Description:
------------
Running commands with shell_exec in browser is working very slower than CLI. I'm 
having same problem with system() and proc_open(). 

Running from shell takes 0.11 sec, but running from browser takes 16.96 second. 
I tested out same code in Linux Ubuntu, same problem happens. 

CLI
------------

float(0.11125087738037)
string(211) "graph_left = 67
graph_top = 33
graph_width = 800
graph_height = 200
image_width = 882
image_height = 273
graph_start = 1310835249
graph_end = 1310921349
value_min = 0.0000000000e+00
value_max = 1.1000000000e+00
"

Browser / Apache
------------

float 16.960417032242
string 'graph_left = 67
graph_top = 33
graph_width = 800
graph_height = 200
image_width = 882
image_height = 273
graph_start = 1310834364
graph_end = 1310920464
value_min = 0.0000000000e+00
value_max = 1.1000000000e+00
' (length=211)

Test script:
---------------
<?php

$start = microtime(1);
$output = shell_exec($executor->getCommandString());
$end = microtime(1);
var_dump($end - $start, $output);