echo 5*5 but more complex

chadsmith76

Hello,

I want to do the below

$text1= 'what is 5 * 5';

$text2=str_replace("what is","",$text1);
$text2=str_replace(" ","",$text2);

//so now $text2 = 5*5

echo $text2;

I want it to echo 25 the answer to 55 but instead it just echos 55.

I want to build a calculator with one input box, strip out any other text to only be left with the math problem, then have php calculate the answer like google's calculator.

I guess maybe it would be possible with javascript to write to the file to have a true echo 5 * 5 rater than echo $text2 but is there a way to do this all within php??

Thanks.

SargeZT

The easiest way to do it is:

<?php
$text1= 'what is 5 * 5';
$text2=str_replace("what is","",$text1);
$text2=str_replace(" ","",$text2);
$result = FALSE;
//so now $text2 = 5*5
eval("\$result=".$text2.";");
echo $result;
?>

But, I'd seriously, SERIOUSLY reccomend adding some input validation in there.

_theworks

echo 'what is 5*5 ?'.5 * 5.'maybe?';

umm im probably not getting ur question but u cant use javascript to write to files on the server as it runs on the clients machine.

chadsmith76

Thanks, that is just what I was looking for.

Validation so the user couldnt enter invalid characters? How would I do that?

Sorry I am just learning this sort of thing, and didnt find any useful tutorials for what i want.

Thanks for any help you can give.

Chad

_theworks

ummmm well its a simple concept. but how you go about doing it will make or break your app (i just wanted to say that)😃

ok after you post the info to the phpscript you want the script to strip the input string of all the characters you dont want...

chadsmith76

How can i strip out all a-zA-Z characters. I think i can use str_replace but i just can figure out the correct way to put it

str_replace("*[a-zA-Z]","",$var)

is what i have now but its not working?? I have tried a few differnet variations but no luck.

thanks

_theworks

use [man]preg_replace[/man]

chadsmith76

so just switch the str_replace iwht preg_replace and the code i have will work?

chadsmith76

yes it worked, i had to change it sa bit to this "^{[a-zA-Z]^"}

another question is how can i do percentages, will preg_replace let me choose any number before a % sign and move the decimal place to the left two places? Or will php do % math??

Thanks for all your guys help.

_theworks

you mite want to look at Operators