Store the variable using this name. keys are cache-unique, so storing a second value with the same key will overwrite the original value.
The variable to store
Time To Live; store var in the cache for ttl seconds. After the ttl has passed, the stored variable will be expunged from the cache (on the next request). If no ttl is supplied (or if the ttl is 0), the value will persist until it is removed from the cache manually, or otherwise fails to exist in the cache (clear, restart, etc.).
Names in key, variables in value.
Returns true on success or false on failure. Second syntax returns array with error keys.