Can I parse and analyse text which has been entered into a text field?

Yes, you can get the value in the text boxes and send or redirect the data to a PHP file.

Please check these 2 helpful guides:
How-to-Post-Submission-Data-to-Thank-You-Page
Send-POST-Data-From-JotForm-Using-PHP-in-Custom-Thank-You-Page

If you are planning to copy the value entered on 1 text field to another then you can use the "Update/Calculate Field" conditions. Please check this guide: How-to-Populate-Field-with-a-Value-from-another-Field

If this is not what you need, then please let us know and provide more details about your issue. Thank you.