Vertical lines on screen.

I don’t know how it happened and it’s been a long time since it first appeared.

Whenever I turn on my iPhone 4 vertical lines shows up different colors and you can’t see the wallpaper or anything. It occupies the whole screen and looks like the Matrix or something. The lines always moved vertically also. And looked like it’s glitching. I don’t know what’s wrong cause my screen is perfectly fine. Any idea what’s the problem? And how should I solve it? My phone is not covered by warranty anymore.

Thanks.