Migration Symfony 1.2.1 -> 1.4.11

At what should I need to be careful when I migrate a project made in with开发者_如何学运维 Symfony 1.2.1 to Symfony 1.4.11 ?

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You should follow the instructions here: http://www.symfony-project.org/tutorial/1_4/en/upgrade

There is a validator which you can run on your code that will tell you which files have code that needs to be changed. Also, remember since you want to go from 1.2.1 -> 1.4.11, you will first need to upgrade to 1.3. So you would run:

$ php symfony project:upgrade1.3

and then switch to 1.4.