youtube-dl apache / php问题

Question

I installed the lastest version of youtube-dl and it works perfectly via the terminal but not via the web.

Terminal: (Works perfectly. Downloads the video.)

[****@****** bin]# /opt/ActivePython-2.7/bin/python /usr/bin/youtube-dl-test -g http://www.youtube.com/watch?v=d3rzmQqVszo

And it works with php via the terminal: (Works. Downloads video)

[****@****** ****]# php test.php

But it fails when I visit it via the web. http://sifdsfdfdf.com/test.php

PHP script: (Fails. Blank page.)

$url=exec("/opt/ActivePython-2.7/bin/python /usr/bin/youtube-dl-test -g http://www.youtube.com/watch?v=d3rzmQqVszo");
echo $url;

Error log:

Traceback (most recent call last):
  File "/opt/ActivePython-2.7/lib/python2.7/runpy.py", line 162, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/opt/ActivePython-2.7/lib/python2.7/runpy.py", line 72, in _run_code
    exec code in run_globals
  File "/usr/bin/youtube-dl-test/__main__.py", line 15, in <module>
  File "/usr/bin/youtube-dl-test/youtube_dl/__init__.py", line 70, in <module>
  File "/usr/bin/youtube-dl-test/youtube_dl/utils.py", line 5, in <module>
  File "/opt/ActivePython-2.7/lib/python2.7/ctypes/__init__.py", line 549, in <module>
    CFUNCTYPE(c_int)(lambda: None)
MemoryError

Thanks