You have two classes with same name, did you copy classes from ezflow into your own extension and forgot rename the class? Or is the file corrupted, or, or..? Many possibilities, search for "class eZFlowPool" in all php files to see where else it has been declared.
"first, regenerate your autload with php bin/php/ezpgenerateautoloads.php -e"
Hy,
re-generating the autoload is one of the few basic things you should know when using/programming eZPublish.
First you need a commandline (shell) on your Server where your eZPublish is running (or your development server). Then go into (change directory) the folder, where you have eZPublish installed and type as non-root (Administrator) User: "php bin/php/ezpgenerateautoloads.php -e" which will create a "mapping" of php-Class-names and the corresponding location of php-files.
This is very similar when on linux, mac or windows. Sometimes you might require to use the full path to the "php" binary (the program, or exe file). So instead of typing "php bin/php/ezpg..." you might consider using "/usr/bin/php bin/php/ezpg..." or on Windows "C:\Program Files\php5\bin\php.exe bin\php\ezpg..." or wherever you have php installed.
As always: Do not copy'n'paste anything you find on the net into your shell. Make sure you understand what these commands do. If not doing so, yopu might have more problems then you have now.
