Here is a quick tip that will show several methods how you can install pear beta packages. Normally if you will try to install a pear package that has not released yet a stable version, you will receive an error like:
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pear install Translation2
Failed to download pear/Translation2 within preferred state "stable", latest release is version 2.0.0RC3, stability "beta", use "channel://pear.php.net/Translation2-2.0.0RC3" to install
Cannot initialize 'channel://pear.php.net/Translation2', invalid or missing package file
Package "channel://pear.php.net/Translation2" is not valid
install failed
Method 1: The classic way - to set the preferred_state beta