Making fast code - General issues

Anon

Hello,

I'm new to PHP and programming in general and I'd like to write fast code :

is there any difference in speed execution between :

echo "something" and print "something" ?

echo 'something' and echo "something" ?

IF, ELSEIF, ELSE loop and CASE loop ?

a program structured like
<?php
PHP Code
echo "<HTML Tags........."
echo "</HTML Tags........"
PHP Code
?>

and

<?php PHP Code ?>
<HTML Tags....>
<?php PHP Code ?>

Thank you for your help.

Eric.

Anon

of course the code outside the PHP tags will not be executed by PHP compiler, but directly to the web browser.

But the difference is in milli seconds i guess, so it doesnt really make any difference, unless you have a page with 1000's of lines of HTML code generation, then it might make a difference of second or 2.

the time of loops, whether its FOR, IF, WHILE, SWITCH etc, really depends on the complexity of the loop you have. this issure is quite complex and we have systems like Big O notation etc. to find out the time of the code's running. But then again they vary from milliseconds or so.

if you say:

$num = 5;
for ($i=0; $i<$num; $i++) {
...
}

while ($i<$num) {
...

$i++
}

etc.. would not make any difference at all, because the number of loop is so low that you wont notice any difference.

Anon

Also note the differns in the

echo "bla";
echo 'bla';
print "bla";

echo "" and print "" does excacly the same thing. But echo '' does not parse to stuff inside the ''... so if you want the output to contain a variable you would have to write either

$mystring = "world";
echo/print "Hello $mystring!!!";

$mystring = "world";
echo 'Hello ' . $mystring . '!!!';

Andreas Bernhardsen
Graficonn

Anon

Only the implementors of PHP can really tell what is faster or slower I guess.

Switch/case should be faster than if/else constructs - I think 😉 It is mostly not the speed that makes the difference when selecting loops. It is how and when the evaluation occur in a loop construct. Be careful to design your loops and algorithms in a good way. I should add that doing, for example, sql selects to databases are so much more overhead than handling strings - but...

The general rule is to avoid parsing if it is not needed, either code or text. Thus plain html, where applicable, should always be faster since the parser only needs to find the next <?php

I don't really know about print/echo/printf speed differences. But if you use double quotes around a string it gets interpreted (the parser searches for backslashes, variables etc). When using single quotes the string is treated exactly as written. Therefore using single quotes around the string is faster.

Anon

A few comments... switch/case is not always faster than if/else, this aplies mostly when you don't got that many diffrent cases..
i.e.

if($var == 1)
{
.....
}
else if($var == 2)
{
.....
}
else
.....

is faster than

switch($var)
{
case 1:
....
break;
case 2:
....
break;
default:
....
}

Switch is faster than if when you have a lot of options. the if statement evaluates eatch and every one until it finds a match. But the switch makes a lookup table and branches directly to the right case...

Andreas Bernhardsen
Graficonn

Anon

They key to writing fast code is to find what sections of your code are eating the most CPU time and causing the most delay, and trying to streamline them.

Generally speaking, the difference between print, printf, sprintf, echo and all is pretty small.

The difference between running 500 small queries at 10 ms each and three big queries at 100ms each is that while those three queries may weigh a lot individually, they can, because there's only three of them.

The real trick is to find the slowest stuff on your site you simply can't get any faster because of complexity, and caching it.

Got an index.php3 that takes 3 seconds to generate? Cron up a wget to snatch it into an index.html every couple of minutes, and point apache at that for the index.