unpredictable results.

I have a web based database with php and mysql. lets say a user types about 300k in a textarea box then clicks submit. not all the text gets submited to mysql. I run the insert command to insert the text at the mysql command line and that works fine. I dont get it. the column type in mysql is blob, largetext, or medium text. IF I type in say 400k in the textarea it would submit say 200k.; IT is unpredictable.This is alot of text but if it picks and choose what it wants to submit then what if it does when someone types in 10K?; this has to work 100% of the time. Say the textarea name is $text. IF pass $text to another file and echo $text that works fine. this is strange. Please help. Mike