Timer

Get the execution time of the script or sql query was executed.

PHP

Start and stop a timer PHP - Stack Overflow

MySQL

Recording the time elapsed after the sql query was executed.

SELECT @timer := CURRENT_TIMESTAMP();
SELECT SLEEP(2); /* sleep 2 seconds for testing purpose */
SELECT 'custom message' AS 'action', CURRENT_TIMESTAMP() AS 'end time', @timer AS 'start time', TIMEDIFF(CURRENT_TIMESTAMP(), @timer) AS 'time elapsed';

Linux command (BASH)

Linux console, macOS Terminal or Cygwin commands on Win

START=$(date +%s)

# sleep 2 seconds for testing purpose
sleep 2s

END=$(date +%s)
DIFF=$(( $END - $START ))
printf "Elapsed time %02dh:%02dm:%02ds\n" $(($DIFF/3600)) $(($DIFF%3600/60)) $(($DIFF%60))

# expected result: 
#   Elapsed time 00h:00m:02s

Python

performance - Measure time elapsed in Python? - Stack Overflow

References