$im = imagecreatetruecolor(400, 300);

# ...

imagejpeg($im, '/tmp/image.jpg');

• imagecreatetruecolor - creates true color lib:GD image object with specified width & height
• imagejpeg - saves $im gd object to the specified 'jpeg' file
• /tmp/image.jpg - path to save jpeg to

group: save_formats