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+Adds all the element arguments to the HyperLogLog data structure stored at the
+variable name specified as first argument.
+
+As a side effect of this command the HyperLogLog internals may be updated to
+reflect a different estimation of the number of unique items added so far (the
+cardinality of the set).
+
+If the approximated cardinality estimated by the HyperLogLog changed after
+executing the command, `PFADD` returns 1, otherwise 0 is returned. The command
+automatically creates an empty HyperLogLog structure (that is, a Redis String of
+a specified length and with a given encoding) if the specified key does not
+exist.
+
+To call the command without elements but just the variable name is valid, this
+will result into no operation performed if the variable already exists, or just
+the creation of the data structure if the key does not exist (in the latter case
+1 is returned).
+
+For an introduction to HyperLogLog data structure check the `PFCOUNT` command
+page.
+
+@return
+
+@integer-reply, specifically:
+
+- 1 if at least 1 HyperLogLog internal register was altered. 0 otherwise.
+
+@examples
+
+```cli
+PFADD hll a b c d e f g
+PFCOUNT hll
+```