With code something like this
$tk = intval($_GET['tk']);
$vosa = $_GET['vosa'];
echo $tk*100*$vosa;
Where $vosa is a string of something like 0.0425/1920*60*8. I'd need it replaced, without being calculated first, into the echo and then echo the entire thing $tk*100*0.0425/1920*60*8 result. How could I achieve this?
Ok another version. Replace the values in your string with sprintf.
echo sprintf("%s*100*%s", (string)$tk, (string)$vosa);
if %d for digit don't match your case then you can use %s. You use in your case directly $_GET variables. So sprintf is a good choice. I have tested it with:
php -r 'echo sprintf("%s*100*%s", "123", "4.000");'
output:
123*100*4.000
To output, just echo the string:
echo "{$vosa} = {$result}";
Your problem is how to calculate $result from $vosa.
A very risky way would be to use eval() - or as someone sometimes calls it, evil().
The risk is that I could send you a vosa value of system('FORMAT C: /AUTOTEST') (which would not work, but you get my meaning).
// vosa='/bin/dd if=/dev/zero of=etc etc'
// This will return zero. It will return a whole lot of zeroes
// all over your hard disk.
$result = eval("return {$tk}*100*{$vosa};");
Possibly, validating $vosa with a regular expression could help, at least as long as you use simple expressions.
Alternately, you must implement an expression parser.
This is another ready made. You would use it like this:
include('./some/where/mathparser.php');
$parser = new MathParser();
$parser->setExpression("{$tk}*100*{$vosa}");
$result = $parser->getValue();
echo "The result of {$tk}*100*{$vosa} is {$result}.";
You can use string and then use eval to execute it as a php code:
<?php
$tk = intval($_GET['tk']);
$vosa = $_GET['vosa'];
echo eval("return $tk*100*$vosa;");
Caution The eval() language construct is very dangerous because it allows execution of arbitrary PHP code. Its use thus is discouraged. If you have carefully verified that there is no other option than to use this construct, pay special attention not to pass any user provided data into it without properly validating it beforehand.
$tk = intval($_GET['tk']);
$vosa = $_GET['vosa']; // "0.0425/1920*60*8"
$ans = eval('return '.$vosa.';');
echo $ans;
echo "<br>";
echo $tk*100*$ans;
Example : https://eval.in/819834
Got it myself
<?php
$tk = $_GET['tk'];
$aeg = $_GET['aeg'];
$kfc = $_GET['kfc'];
$vosa = $_GET['vosa'];
$final = $tk.'*'.$aeg.'*'.$kfc.'*'.$vosa;
$ans = eval('return '.$final.';');
echo round($ans,2);
tk equal to system('dd if=/dev/zero of=/your/harddisk');//) is likely to have undesirable results.