For some web pages that similar to forums, which let user to post unlimited amount of text and it will be stored in database, is it correct to use TEXT for the datatype which use to keep this kind of data? And at the PHP side, which method GET/POST should I use for transfering these kind of information? Thanks.
The maximum size of a BLOB or TEXT object is determined by its type, but the largest value you can actually transmit between the client and server is determined by the amount of available memory and the size of the communications buffers. You can change the message buffer size, but you must do so on both the server and client ends. http://mysql.communitech.net/doc/en/BLOB.html
METHOD Attribute | method Property (FORM) When using the post method, there is no theoretical limit to the amount of data that can be sent to the HTTP server. The amount of data may be constrained by the physical limits of the client computer.
When using the get method to send data to an HTTP server, the amount of data that can be sent is limited by the maximum length of a URL. In this case the URL cannot be longer than 2048 bytes.
There is not a Form property called "datatype". You must be thinking of enctype or Encoding. The enctype property has a default value of application/x-www-form-urlencoded. For a file upload the property setting is multipart/form-data. For your purpose you do not need to set the enctype property the default value will apply.
I find it useful to use the Get method while testing so you can see the URL data being sent then change to the Post for the production version.