after installing PHP gd library: when trying to run any PHP parsed page, a save dialog appears

I've tried to install GD library on PHP5:

sudo apt-get install php5-gd

Next,

sudo service apache2 restart

After that, when trying to run any PHP parsed page, a save dialog appears.

You can see screenshot:

I've tried to run phpinfo.php page, but same issue:

enter image description here

P.S :

$ php -i | grep -i --color gd

gd Output test results:

PHP Warning:  Unknown: It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected the timezone 'UTC' for now, but please set date.timezone to select your timezone. in Unknown on line 0
gd
GD Support => enabled
GD Version => 2.1.0-alpha
gd.jpeg_ignore_warning => 0 => 0
GDMSESSION => ubuntu
_SERVER["GDMSESSION"] => ubuntu

I'm using LAMP server on Linux/Ubuntu 12.04

Solution

I had a similar problem in a server deployment not too long ago.

My issue was solved by executing the command:

sudo apt-get install libapache2-mod-php5

Post in the comments below if it doesn't work. Also, reboot your computer after executing this command (so all of the services are restarted), to make things simple.