Fatal error in Magento 1.9

[saad _ahmad]

The issue I'm facing is the Magento Admin Panel. When i try to view the order. It gives the following error. I'm newbie. I don't know how to solve this issue. Thanks 

[Vimal Kumar]

Hi @saad _ahmad,

Which Magento and php version you are using?

[saad _ahmad]

I'm using magento 1 php version 5