\$cache\_lifetime {#variable.cache.lifetime}

This is the length of time in seconds that a template cache is valid. Once this time has expired, the cache will be regenerated.

• `$caching` must be turned on (either Smarty::CACHING\_LIFETIME\_CURRENT or Smarty::CACHING\_LIFETIME\_SAVED) for `$cache_lifetime` to have any purpose.
• A `$cache_lifetime` value of -1 will force the cache to never expire.
• A value of 0 will cause the cache to always regenerate (good for testing only, to disable caching a more efficient method is to set $caching = Smarty::CACHING\_OFF).
• If you want to give certain templates their own cache lifetime, you could do this by setting $caching = Smarty::CACHING\_LIFETIME\_SAVED, then set `$cache_lifetime` to a unique value just before calling display() or fetch().

If $force_compile is enabled, the cache files will be regenerated every time, effectively disabling caching. You can clear all the cache files with the clear_all_cache() function, or individual cache files (or groups) with the clear_cache() function.