PHP Speed - Many Echos vs Building a String

问题:

Wondering if anyone knows if either of these methods would produce an output faster:

Method 1
for ($i=1;$i<99999;$i++) {
echo $i, '<br>';
}

or

Method 2
for ($i=1;$i<99999;$i++) {
$string .= $i . '<br>';
}
echo $string;

Thanks for any input you have.

回答1:

Method 1 seems like it'd be faster. Method 2 will have to spit out a bunch of CONCAT opcodes for each iteration of the loop, and the very long string will be built in memory until you're ready to send it. Method 1 on the other hand will just be two ECHO opcodes per loop, and then PHP/your webserver is free to flush content to the client before you've fully finished, if it wants to.

Of course, if you're concerned about micro-optimisation, you're going to get far better performance by using an opcode cache, caching proxy, or something like hiphop.

回答2:

Method 1 Uses less Memory and CPU and is "faster" (Less server load) But the output bottleneck most likely is the browsers downloadspeed.

If you don't buffer the output, the browser can start downloading stylesheets, images, etc sooner.
(while your script is waiting for some query results)

Check out the answers on PHP Optimalization or http://code.google.com/speed/articles/optimizing-php.html for more tips.

回答3:

I have read that the fastest method is to enable output buffering and do many echoes. I don't have benchmarks to confirm this claim, though.

Anyway, I think this is in the realm of micro-optimization. The difference is probably measurable, but insignificant. As @Coronatus comments above, if your app were that sensitive to performance, you wouldn't be using PHP!

回答4:

If you wan to micro-optimise, look to changing $i++ to ++$i as well