Read this article first: Simple PHP OCR with GD

Step 1:
Goto we can see many pictures contain telephone number. We find that these pictures that contain a maximum of 11 digits, and have the same font, same size.

We use 3 pictures contain all number from 0 to 9:

Step 2:
In this article PHP: Crop image function (part 2), we croped a picture to a piece of size 7×10 px
Now, we use 3 pictures above, we get 10 pictures below:

Note: we can use Photoshop to crop picture

Step 3:
Read pixel