NetBeans: Code folds do not appear on one of my PHP files

I'm using the NetBeans IDE. Normally, every PHP file in my project has code folds:

However, one PHP file in my project doesn't have code folds:

The file has no syntax errors. I've tried restarting NetBeans and reopening the project and the folds still do not appear. What could it be?

More info:

• I'm using NetBeans IDE 7.0.1.
• The file's extension is .php like all the PHP files in my project.
• On another file which has the same content exactly, code folds appear.

Follow the following steps:

1) open netbeans 2) select tool => options 3) select Editor tab and General sub tab 4) and check code fold check box

Find attached image for detail.