Problem changing directory with Exec()

[Anon]

I am running red hat on the web sever.

$filepath" /home/norgem/www/content/images"
echo "filepath is: $filepath";

$chdir = exec("cd $filepath");

$chdir = exec("pwd");

echo "$chdir";

The current directory comes out as:
the one i was originally in:
/home/norgem/www/admin

Why???