Question

I’m trying to prevent caching by appending a ‘? t=’ to the end of my JS files. What’s the fastest way to get such a number? time() or rand() or something else?

Answer 1

time() and mt_rand() are pretty similar in terms of efficiency in PHP – you select one or the other based on what factors you need it for:

• Just hard to guess: use mt_rand() (e.g., generating use salt)
• Get a unique identifier that is hard to guess: use mt_rand(1, 931415926536); (e.g., generating session id)
• (obviously) keep records: use time() (e.g., prevent caching, logs etc)

If you really want to know, time() is slightly faster—but you really don’t need to worry about it. (It’s the difference between one or two small parts of a second.)

Note that rand() is now an alias to mt_rand() since PHP 7.1:

rand() and srand() have now been made aliases to mt_rand() and mt_srand(), respectively. This means that the output for the following functions have changed: rand(), shuffle(), str_shuffle(), and array_rand().

You probably know this already, but be sure to always profile your code before making optimizations; often it’ll run slowly for reasons completely different than what you expected.