php maximum characters in text field

Is there a maximum number of character $_POST will/can return from a text field. I have an online form that was driving me nuts trying to troubleshoot, as most orders were coming in fine, but this one would not. I narrowed down to the length of the "customer description" field which has no limits on the form or in the database. I was told there was a limit to how much $_POST could return. Can someone advise? Thanks! Trish