I broke my site

In case any of the scripts you injected broke your site in a terrible way (not resolvable trough the concrete5 admin panel) you have to delete the Block contents from the database.

Delete the content of all Easy PHP Blocks with SQL: "UPDATE fwEasyPhp SET php = '';"

You can also browse your database with phpMyAdmin or your tool of choice and locate the entry which you think is responsible for the errors and fix it right there in the table fwEasyPhp.