[Codeigniter][solved] Disallowed Key Characters

While i was writing php, suddenly appear an error message with a blank page.

Disallowed Key Characters.

And found the reason why to cause this problem:

I missed a end- double quotation marks in the html input tag.
After changing the sentence from :

<input type="checkbox" name="type_1 value="1" />

to

<input type="checkbox" name="type_1" value="1" />

The error stopped.

About the reason why caused this problem :
It's because the Codeigniter can not get the name field in right format to make a correct SQL for database.