Can send requests to Arduino but not getting replies

The weirdest thing ever. I'm using PHP on a Fedora 10 machine to communicate with my Arduino, I'm opening the serial connection using fopen('/dev/ttyUSB0', "r+"). When I'm writing to the open file the Arduino actually replies BUT I only see it in the Arduino IDE Serial Console. When I'm trying to read the file using PHP's fgets($f); I'm getting nothing (even when the IDE is closed).

Any ideas? Thanx