6 ms·

40 Tips for optimizing your php Code

13 points by raindoll 19y ago

some 19y ago
> 1. If a method can be static, declare it static. Speed improvement is by a factor of 4. Wow! function Prime1() { ...calc one million prime numbers...} static function Prime2() { ...calc one million prime numbers...} Prime2() will calculate the prime numbers 4 times faster then Prime1()? Cool.
some 19y ago
> Set the maxvalue for your for-loops before and not in the loop. What does this mean?
- raindoll 19y ago
  it means that this: $maxvalue = 100/10; for($i=0; $i<$maxvalue; $i++){ // Some code } is much faster than this: for($i=0; $i<100/10; $i++){ // Some code } because the value is calculated once instead of ten times.
  - some 19y ago
    Ok. The same comes again at point 15: > Do not use functions inside of for loop, such as for ($x=0; $x < count($array); $x) The count() function gets called each time.
  - ratsbane 19y ago
    That's not necessarily true. If the compiler is smart enough it won't recalculate the value of a numeric expression which doesn't contain any variables. On the other hand, dereferencing a variable isn't without cost. Of course, in most cases you'd be dereferencing variables anyway in the test clause, so the original idea, compute loop limits before entering the loop, is correct.: mbp:~/test doug$ time php -r 'for ($i=1; $i<100000000/10; $i++) {$x++;};' real 0m5.930s user 0m5.867s sys 0m0.026s mbp:~/test doug$ time php -r '$maxval=100000000/10; for ($i=1; $i<$maxval; $i++) {$x++;};' real 0m6.999s user 0m6.907s sys 0m0.029s mbp:~/test doug$ time perl -e 'for ($i=1; $i<100000000/10; $i++) {$x++;}' real 0m2.520s user 0m2.496s sys 0m0.010s mbp:~/test doug$ time perl -e '$maxval=100000000/10; for ($i=1; $i<$maxval; $i++) {$x++;}' real 0m2.537s user 0m2.499s sys 0m0.014s The results are a little different with Python (maxval1.py computes inline; maxval2 divides in advance and uses variable inline) mbp:~/test doug$ time python maxval1.py real 0m2.134s user 0m1.761s sys 0m0.276s mbp:~/test doug$ time python maxval2.py real 0m1.890s user 0m1.588s sys 0m0.278s Java shows even more of a difference (again, maxval2 sets variable in advance): mbp:~/test doug$ time java maxval1 real 0m0.174s user 0m0.116s sys 0m0.040s mbp:~/test doug$ time java maxval2 real 0m0.531s user 0m0.125s sys 0m0.041s
    - andreyf 19y ago
      Does anyone have any ideas for what's happening in the Python example? Could you post the Python code?
      - ratsbane 19y ago
        Sure... here is maxval1.py: for i in range(1, 100000000/10): pass And here is maxval2.py: maxval=100000000/10 for i in range(1, maxval): pass
        andreyf 19y ago
        Oh, of course - range() is evaluated once in either case. It returns an array, which is then stepped through. The time difference must have been just some inaccuracy. I guess 'time' isn't the best command to use to test efficiency ... or maybe try adding another 0?
        ratsbane 19y ago
        Oh, thanks. I redid it using xrange instead of range and the numbers went down to an average (over 20 tries) of about 1.36 sec for maxval1 (which computes endpoint within the xrange) and 1.9 sec for maxval2 (which uses variable in xrange.)
    - ratsbane 19y ago
      Here is the java code too. First maxval1.java: public class maxval1 { static int $i, $x; public static void main(String args[]) throws Exception { for ($x=$i=1; $i<100000000/10; $i++) {$x++;} System.out.println($x); } } And maxval2.java: public class maxval2 { static int $a, $i, $x; public static void main(String args[]) throws Exception { $a=100000000/10; for ($x=$i=1; $i<$a; $i++) {$x++;} System.out.println($x); } }
jbyers 19y ago
These range from sensible to utterly useless [1,2,3]. I'd say forget all of this and focus on being a productive developer, building something people want, and ruthlessly avoiding premature optimization. When your application is slow, measure it to find out why, then fix it, and repeat. 1. Let's take #2, "echo is faster than print" - Seriously, is this what we should be worrying about? I can't detect a difference in PHP 5.2.4 across 100,000 echos/prints, so it must not be very big. 2. ++i vs i++ to squeeze out 1 fewer opcode? 3. Using isset($foo{5}) vs a strlen check? I pity the next programmer who has to read and understand the purpose of this code.

13 points by raindoll 19y ago

some 19y ago

> 1. If a method can be static, declare it static. Speed improvement is by a factor of 4. Wow! function Prime1() { ...calc one million prime numbers...} static function Prime2() { ...calc one million prime numbers...} Prime2() will calculate the prime numbers 4 times faster then Prime1()? Cool.

some 19y ago

> Set the maxvalue for your for-loops before and not in the loop. What does this mean?

raindoll 19y ago
it means that this: $maxvalue = 100/10; for($i=0; $i<$maxvalue; $i++){ // Some code } is much faster than this: for($i=0; $i<100/10; $i++){ // Some code } because the value is calculated once instead of ten times.
- some 19y ago
  Ok. The same comes again at point 15: > Do not use functions inside of for loop, such as for ($x=0; $x < count($array); $x) The count() function gets called each time.
- ratsbane 19y ago
  That's not necessarily true. If the compiler is smart enough it won't recalculate the value of a numeric expression which doesn't contain any variables. On the other hand, dereferencing a variable isn't without cost. Of course, in most cases you'd be dereferencing variables anyway in the test clause, so the original idea, compute loop limits before entering the loop, is correct.: mbp:~/test doug$ time php -r 'for ($i=1; $i<100000000/10; $i++) {$x++;};' real 0m5.930s user 0m5.867s sys 0m0.026s mbp:~/test doug$ time php -r '$maxval=100000000/10; for ($i=1; $i<$maxval; $i++) {$x++;};' real 0m6.999s user 0m6.907s sys 0m0.029s mbp:~/test doug$ time perl -e 'for ($i=1; $i<100000000/10; $i++) {$x++;}' real 0m2.520s user 0m2.496s sys 0m0.010s mbp:~/test doug$ time perl -e '$maxval=100000000/10; for ($i=1; $i<$maxval; $i++) {$x++;}' real 0m2.537s user 0m2.499s sys 0m0.014s The results are a little different with Python (maxval1.py computes inline; maxval2 divides in advance and uses variable inline) mbp:~/test doug$ time python maxval1.py real 0m2.134s user 0m1.761s sys 0m0.276s mbp:~/test doug$ time python maxval2.py real 0m1.890s user 0m1.588s sys 0m0.278s Java shows even more of a difference (again, maxval2 sets variable in advance): mbp:~/test doug$ time java maxval1 real 0m0.174s user 0m0.116s sys 0m0.040s mbp:~/test doug$ time java maxval2 real 0m0.531s user 0m0.125s sys 0m0.041s
  - andreyf 19y ago
    Does anyone have any ideas for what's happening in the Python example? Could you post the Python code?
    - ratsbane 19y ago
      Sure... here is maxval1.py: for i in range(1, 100000000/10): pass And here is maxval2.py: maxval=100000000/10 for i in range(1, maxval): pass
      - andreyf 19y ago
        Oh, of course - range() is evaluated once in either case. It returns an array, which is then stepped through. The time difference must have been just some inaccuracy. I guess 'time' isn't the best command to use to test efficiency ... or maybe try adding another 0?
        ratsbane 19y ago
        Oh, thanks. I redid it using xrange instead of range and the numbers went down to an average (over 20 tries) of about 1.36 sec for maxval1 (which computes endpoint within the xrange) and 1.9 sec for maxval2 (which uses variable in xrange.)
  - ratsbane 19y ago
    Here is the java code too. First maxval1.java: public class maxval1 { static int $i, $x; public static void main(String args[]) throws Exception { for ($x=$i=1; $i<100000000/10; $i++) {$x++;} System.out.println($x); } } And maxval2.java: public class maxval2 { static int $a, $i, $x; public static void main(String args[]) throws Exception { $a=100000000/10; for ($x=$i=1; $i<$a; $i++) {$x++;} System.out.println($x); } }

jbyers 19y ago

These range from sensible to utterly useless [1,2,3]. I'd say forget all of this and focus on being a productive developer, building something people want, and ruthlessly avoiding premature optimization. When your application is slow, measure it to find out why, then fix it, and repeat. 1. Let's take #2, "echo is faster than print" - Seriously, is this what we should be worrying about? I can't detect a difference in PHP 5.2.4 across 100,000 echos/prints, so it must not be very big. 2. ++i vs i++ to squeeze out 1 fewer opcode? 3. Using isset($foo{5}) vs a strlen check? I pity the next programmer who has to read and understand the purpose of this code.