Flex :: DataGrid Reads A Field From LastResult.node As Number?

Why does Flex 3 DataGrid read a string from XML lastResult.node as number?A field is saved as var_char in mysql, php reads it as string and pass it OK.If there are more then 16 charaters it gets rounded....For example:

this in database cell:

12345678901234567

gets read in DataGrid as nubmer as 12345678901234568

this is in database cell:

5555544444222223333377777

php reads it same and puts it in XML flex reads XML into arrayCollection and DataGrid reads it as:

5.55554444422222e+24

So it reads it as number, why? And how to make it read as String? I tried with labelFunction, no help.