Magento & Memcached - Fix "Unknown number format type 'boolean'."
Recently, I posted a guide to speed up Magento using Memcached. If you've followed another guide that has incomplete information, Magento may fail to work, greeting you with a rather unhelpful error message "Unknown number format type 'boolean'. Format '' must be a valid number format string.". The fix for this is simple.
To fix this error message, edit your app/etc/local.xml configuration file and find the <backend>memcached</backend> element, then add another element at the same level, specifying a prefix, such as "MAGE_": <prefix>MAGE_</prefix>. Here's what my XML looks like:
<global> ... <cache> <backend>memcached</backend> <prefix>MAGE_</prefix> <memcached> ... </memcached> </cache> ... </global>
The prefix exists to make sure that multiple Magento installations using the same cache provider don't overwrite each other's cache entries. If you do actually run multiple Magento installations and they use the same Memcached server for caching, make sure they each have a different value for the <prefix> setting.