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PHP Newbie can't evaluate numerical string as number

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  PHP Newbie can't evaluate numerical string as number "Graham" <graham.stow@stowassocs.co.uk> - 2011-11-07 16:25 +0000
    Re: PHP Newbie can't evaluate numerical string as number The Natural Philosopher <tnp@invalid.invalid> - 2011-11-07 16:56 +0000
    Re: PHP Newbie can't evaluate numerical string as number Denis McMahon <denismfmcmahon@gmail.com> - 2011-11-07 17:52 +0000
      Re: PHP Newbie can't evaluate numerical string as number "Graham" <graham.stow@stowassocs.co.uk> - 2011-11-08 08:41 +0000
        Re: PHP Newbie can't evaluate numerical string as number Erwin Moller <Since_humans_read_this_I_am_spammed_too_much@spamyourself.com> - 2011-11-08 09:56 +0100
          Re: PHP Newbie can't evaluate numerical string as number "Graham" <graham.stow@stowassocs.co.uk> - 2011-11-08 09:35 +0000
            Re: PHP Newbie can't evaluate numerical string as number Denis McMahon <denismfmcmahon@gmail.com> - 2011-11-08 09:57 +0000
              Re: PHP Newbie can't evaluate numerical string as number Tim Streater <timstreater@greenbee.net> - 2011-11-08 10:08 +0000
                Re: PHP Newbie can't evaluate numerical string as number Denis McMahon <denismfmcmahon@gmail.com> - 2011-11-08 17:49 +0000
              Re: PHP Newbie can't evaluate numerical string as number "Graham" <graham.stow@stowassocs.co.uk> - 2011-11-08 10:27 +0000
    Re: PHP Newbie can't evaluate numerical string as number Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2011-11-07 23:49 +0100
    Re: PHP Newbie can't evaluate numerical string as number Jonathan Stein <jstein@image.dk> - 2011-11-08 11:19 +0100

#3707 — PHP Newbie can't evaluate numerical string as number

I'm a Perl veteran (well almost!) but a PHP newbie. I've got a simple 
subtraction formula in 'vars.php' as follows:

<?php
$formula = "!big_number - !small_number";
?>

I then include it in 'test.php' along with a few variables, do a bit of 
string replacement, run eval on it, then print it

<?PHP
include 'vars.php';
$big_number = 30000;
$small_number = 3000;
$formula = str_replace("!", "$", $formula);
eval("\$formula = \"$formula\";");
//$formula = intval($formula);
//settype($formula, "integer");
print ("formula = $formula\n");
?>

The above gives me...'formula = 30000 - 3000'
when of course what I want is...'formula = 27000'

A few of the many things I've tried are commented out. Please put me out of 
my misery someone!

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#3708

Graham wrote:
> I'm a Perl veteran (well almost!) but a PHP newbie. I've got a simple 
> subtraction formula in 'vars.php' as follows:
> 
> <?php
> $formula = "!big_number - !small_number";
> ?>
> 
> I then include it in 'test.php' along with a few variables, do a bit of 
> string replacement, run eval on it, then print it
> 
> <?PHP
> include 'vars.php';
> $big_number = 30000;
> $small_number = 3000;
> $formula = str_replace("!", "$", $formula);
> eval("\$formula = \"$formula\";");
> //$formula = intval($formula);
> //settype($formula, "integer");
> print ("formula = $formula\n");
> ?>
> 
> The above gives me...'formula = 30000 - 3000'
> when of course what I want is...'formula = 27000'
> 
> A few of the many things I've tried are commented out. Please put me out of 
> my misery someone!
> 
> 
> 
why not parse $formula using sscanf?

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#3709

On Mon, 07 Nov 2011 16:25:42 +0000, Graham wrote:

> I'm a Perl veteran (well almost!) but a PHP newbie. I've got a simple
> subtraction formula in 'vars.php' as follows:
> 
> <?php
> $formula = "!big_number - !small_number"; ?>
> 
> I then include it in 'test.php' along with a few variables, do a bit of
> string replacement, run eval on it, then print it
> 
> <?PHP
> include 'vars.php';
> $big_number = 30000;
> $small_number = 3000;
> $formula = str_replace("!", "$", $formula); eval("\$formula =
> \"$formula\";");
> //$formula = intval($formula);
> //settype($formula, "integer");
> print ("formula = $formula\n");
> ?>
> 
> The above gives me...'formula = 30000 - 3000' when of course what I want
> is...'formula = 27000'
> 
> A few of the many things I've tried are commented out. Please put me out
> of my misery someone!

Does the following working example help?

<?php

$big_number = 50000;
$small_number = 5000;

$formula1 = "\$result1 = \$big_number - \$small_number;";
$formula2 = "return(\$big_number - \$small_number);";

echo "\$formula1 = '{$formula1}'\n";
echo "\$formula2 = '{$formula2}'\n";

eval($formula1);
$result2 = eval($formula2);

echo "\$result1 = {$result1}\n";
echo "\$result2 = {$result2}\n";

?>

Rgds

Denis McMahon

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#3711

Unfortunately not. Here you introduce the formula into the main script, 
whereas I need to introduce it in a separate script (or import it from a 
database) to save me having to amend it countless times if it ever changes. 
Hence me using str_replace to change !big_number to $big_number. Although 
this worked, I was still left with a 'numerical string' which I couldn't 
evaluate. So I guess my question is how do you evaluate a numerical string 
such as '30000 - 3000'?

"Denis McMahon" <denismfmcmahon@gmail.com> wrote in message 
news:4eb81acf$0$28518$a8266bb1@newsreader.readnews.com...
> On Mon, 07 Nov 2011 16:25:42 +0000, Graham wrote:
>
>> I'm a Perl veteran (well almost!) but a PHP newbie. I've got a simple
>> subtraction formula in 'vars.php' as follows:
>>
>> <?php
>> $formula = "!big_number - !small_number"; ?>
>>
>> I then include it in 'test.php' along with a few variables, do a bit of
>> string replacement, run eval on it, then print it
>>
>> <?PHP
>> include 'vars.php';
>> $big_number = 30000;
>> $small_number = 3000;
>> $formula = str_replace("!", "$", $formula); eval("\$formula =
>> \"$formula\";");
>> //$formula = intval($formula);
>> //settype($formula, "integer");
>> print ("formula = $formula\n");
>> ?>
>>
>> The above gives me...'formula = 30000 - 3000' when of course what I want
>> is...'formula = 27000'
>>
>> A few of the many things I've tried are commented out. Please put me out
>> of my misery someone!
>
> Does the following working example help?
>
> <?php
>
> $big_number = 50000;
> $small_number = 5000;
>
> $formula1 = "\$result1 = \$big_number - \$small_number;";
> $formula2 = "return(\$big_number - \$small_number);";
>
> echo "\$formula1 = '{$formula1}'\n";
> echo "\$formula2 = '{$formula2}'\n";
>
> eval($formula1);
> $result2 = eval($formula2);
>
> echo "\$result1 = {$result1}\n";
> echo "\$result2 = {$result2}\n";
>
> ?>
>
> Rgds
>
> Denis McMahon 

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#3712

On 11/8/2011 9:41 AM, Graham wrote:
> Unfortunately not. Here you introduce the formula into the main script,
> whereas I need to introduce it in a separate script (or import it from a
> database) to save me having to amend it countless times if it ever changes.
> Hence me using str_replace to change !big_number to $big_number. Although
> this worked, I was still left with a 'numerical string' which I couldn't
> evaluate. So I guess my question is how do you evaluate a numerical string
> such as '30000 - 3000'?

I think Dennis showed that trick: use eval().
Personally I think it is ugly, but it works.

example:
$myNumericString = "30000 - 300";
$myEval = '$myResult = '.$myNumericString.';';
eval ($myEval);
echo $myResult;

(not tested)

A warning:
I once had to develop a webside where people needed to enter formula's 
that worked on data (a bit like MS Excel, but serverside).
For example:
"SUM(**somefield**) / COUNT(**somefield**)"
They needed to be stored in a database too, and the number of possible 
manipulations (like SUM and COUNT) were limited.
If I were to eval() that string blindly, I would open up a the side to a 
lot of missery (naughty commands, eg file_put_contents()), so I ended up 
writing a parser that took the formula apart, and if it used anything 
outside my small list of allowed manipulations, I refused the formula.

I am not sure where your formula's come from, but if they are entered by 
users, take some care before using eval().


Regards,
Erwin Moller


>
> "Denis McMahon"<denismfmcmahon@gmail.com>  wrote in message
> news:4eb81acf$0$28518$a8266bb1@newsreader.readnews.com...
>> On Mon, 07 Nov 2011 16:25:42 +0000, Graham wrote:
>>
>>> I'm a Perl veteran (well almost!) but a PHP newbie. I've got a simple
>>> subtraction formula in 'vars.php' as follows:
>>>
>>> <?php
>>> $formula = "!big_number - !small_number"; ?>
>>>
>>> I then include it in 'test.php' along with a few variables, do a bit of
>>> string replacement, run eval on it, then print it
>>>
>>> <?PHP
>>> include 'vars.php';
>>> $big_number = 30000;
>>> $small_number = 3000;
>>> $formula = str_replace("!", "$", $formula); eval("\$formula =
>>> \"$formula\";");
>>> //$formula = intval($formula);
>>> //settype($formula, "integer");
>>> print ("formula = $formula\n");
>>> ?>
>>>
>>> The above gives me...'formula = 30000 - 3000' when of course what I want
>>> is...'formula = 27000'
>>>
>>> A few of the many things I've tried are commented out. Please put me out
>>> of my misery someone!
>>
>> Does the following working example help?
>>
>> <?php
>>
>> $big_number = 50000;
>> $small_number = 5000;
>>
>> $formula1 = "\$result1 = \$big_number - \$small_number;";
>> $formula2 = "return(\$big_number - \$small_number);";
>>
>> echo "\$formula1 = '{$formula1}'\n";
>> echo "\$formula2 = '{$formula2}'\n";
>>
>> eval($formula1);
>> $result2 = eval($formula2);
>>
>> echo "\$result1 = {$result1}\n";
>> echo "\$result2 = {$result2}\n";
>>
>> ?>
>>
>> Rgds
>>
>> Denis McMahon
>
>


-- 
"That which can be asserted without evidence, can be dismissed without 
evidence."
-- Christopher Hitchens

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#3713

Yes it works! (although I admit I'm not entirely sure why). Many thanks! And 
apologies to Denis for having doubted him.

Thanks also for the warning on using formula in this way. The formula in 
question (a bit more complex than A-B) is actually embodied in UK Govenment 
legislation, so I won't be letting users mess with it.

R's
Graham Stow

"Erwin Moller" 
<Since_humans_read_this_I_am_spammed_too_much@spamyourself.com> wrote in 
message news:4eb8eed0$0$6947$e4fe514c@news2.news.xs4all.nl...
> On 11/8/2011 9:41 AM, Graham wrote:
>> Unfortunately not. Here you introduce the formula into the main script,
>> whereas I need to introduce it in a separate script (or import it from a
>> database) to save me having to amend it countless times if it ever 
>> changes.
>> Hence me using str_replace to change !big_number to $big_number. Although
>> this worked, I was still left with a 'numerical string' which I couldn't
>> evaluate. So I guess my question is how do you evaluate a numerical 
>> string
>> such as '30000 - 3000'?
>
> I think Dennis showed that trick: use eval().
> Personally I think it is ugly, but it works.
>
> example:
> $myNumericString = "30000 - 300";
> $myEval = '$myResult = '.$myNumericString.';';
> eval ($myEval);
> echo $myResult;
>
> (not tested)
>
> A warning:
> I once had to develop a webside where people needed to enter formula's 
> that worked on data (a bit like MS Excel, but serverside).
> For example:
> "SUM(**somefield**) / COUNT(**somefield**)"
> They needed to be stored in a database too, and the number of possible 
> manipulations (like SUM and COUNT) were limited.
> If I were to eval() that string blindly, I would open up a the side to a 
> lot of missery (naughty commands, eg file_put_contents()), so I ended up 
> writing a parser that took the formula apart, and if it used anything 
> outside my small list of allowed manipulations, I refused the formula.
>
> I am not sure where your formula's come from, but if they are entered by 
> users, take some care before using eval().
>
>
> Regards,
> Erwin Moller
>
>
>>
>> "Denis McMahon"<denismfmcmahon@gmail.com>  wrote in message
>> news:4eb81acf$0$28518$a8266bb1@newsreader.readnews.com...
>>> On Mon, 07 Nov 2011 16:25:42 +0000, Graham wrote:
>>>
>>>> I'm a Perl veteran (well almost!) but a PHP newbie. I've got a simple
>>>> subtraction formula in 'vars.php' as follows:
>>>>
>>>> <?php
>>>> $formula = "!big_number - !small_number"; ?>
>>>>
>>>> I then include it in 'test.php' along with a few variables, do a bit of
>>>> string replacement, run eval on it, then print it
>>>>
>>>> <?PHP
>>>> include 'vars.php';
>>>> $big_number = 30000;
>>>> $small_number = 3000;
>>>> $formula = str_replace("!", "$", $formula); eval("\$formula =
>>>> \"$formula\";");
>>>> //$formula = intval($formula);
>>>> //settype($formula, "integer");
>>>> print ("formula = $formula\n");
>>>> ?>
>>>>
>>>> The above gives me...'formula = 30000 - 3000' when of course what I 
>>>> want
>>>> is...'formula = 27000'
>>>>
>>>> A few of the many things I've tried are commented out. Please put me 
>>>> out
>>>> of my misery someone!
>>>
>>> Does the following working example help?
>>>
>>> <?php
>>>
>>> $big_number = 50000;
>>> $small_number = 5000;
>>>
>>> $formula1 = "\$result1 = \$big_number - \$small_number;";
>>> $formula2 = "return(\$big_number - \$small_number);";
>>>
>>> echo "\$formula1 = '{$formula1}'\n";
>>> echo "\$formula2 = '{$formula2}'\n";
>>>
>>> eval($formula1);
>>> $result2 = eval($formula2);
>>>
>>> echo "\$result1 = {$result1}\n";
>>> echo "\$result2 = {$result2}\n";
>>>
>>> ?>
>>>
>>> Rgds
>>>
>>> Denis McMahon
>>
>>
>
>
> -- 
> "That which can be asserted without evidence, can be dismissed without 
> evidence."
> -- Christopher Hitchens 

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#3714

On Tue, 08 Nov 2011 09:35:02 +0000, Graham wrote:

> Yes it works! (although I admit I'm not entirely sure why). Many thanks!
> And apologies to Denis for having doubted him.

Heads up - we don't top post in newsgroups. Reply goes at the bottom so 
that reading naturally down the page response is after the comment it 
applies to.

If you read the php manual for eval http://uk.php.net/manual/en/
function.eval.php , all is explained:

There are two ways to get a value from eval into the script that calls 
eval:

a) use return inside the eval code, and assign the value of eval to a 
variable, viz:

$evalResult = eval("return $big_number - $small_number;");
echo $evalResult;

b) assign the result to a variable inside the eval code:

eval("$evalResult = $big_number - $small_number;");
echo $evalResult;

These are the two methods I attempted to show in my example.

Rgds

Denis McMahon

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#3715

In article <4eb8fcf9$0$28445$a8266bb1@newsreader.readnews.com>,
 Denis McMahon <denismfmcmahon@gmail.com> wrote:

> Heads up - we don't top post in newsgroups. Reply goes at the bottom so 
> that reading naturally down the page response is after the comment it 
> applies to.

We? You only speak for yourself.

-- 
Tim

"That excessive bail ought not to be required, nor excessive fines imposed,
nor cruel and unusual punishments inflicted"  --  Bill of Rights 1689

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#3718

On Tue, 08 Nov 2011 10:08:42 +0000, Tim Streater wrote:

> In article <4eb8fcf9$0$28445$a8266bb1@newsreader.readnews.com>,
>  Denis McMahon <denismfmcmahon@gmail.com> wrote:
> 
>> Heads up - we don't top post in newsgroups. Reply goes at the bottom so
>> that reading naturally down the page response is after the comment it
>> applies to.
> 
> We? You only speak for yourself.

I think I can fairly safely claim to speak for the majority of people who 
actually take part in conversations using usenet (as opposed to people 
who use websites which present a web based interface to usenet) when I 
point out that by long standing convention, in usenet, replies go below 
the comments they refer to.

Rgds

Denis McMahon

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#3717

"Denis McMahon" <denismfmcmahon@gmail.com> wrote in message 
news:4eb8fcf9$0$28445$a8266bb1@newsreader.readnews.com...
> On Tue, 08 Nov 2011 09:35:02 +0000, Graham wrote:
>
>> Yes it works! (although I admit I'm not entirely sure why). Many thanks!
>> And apologies to Denis for having doubted him.
>
> Heads up - we don't top post in newsgroups. Reply goes at the bottom so
> that reading naturally down the page response is after the comment it
> applies to.
>
> If you read the php manual for eval http://uk.php.net/manual/en/
> function.eval.php , all is explained:
>
> There are two ways to get a value from eval into the script that calls
> eval:
>
> a) use return inside the eval code, and assign the value of eval to a
> variable, viz:
>
> $evalResult = eval("return $big_number - $small_number;");
> echo $evalResult;
>
> b) assign the result to a variable inside the eval code:
>
> eval("$evalResult = $big_number - $small_number;");
> echo $evalResult;
>
> These are the two methods I attempted to show in my example.
>
> Rgds
>
> Denis McMahon

I hang my head in shame!  Thinking about it, i've been critised for top 
posting before, but couldn't remember the drill as I post to newsgroups so 
rarely. Thanks for being patient and polite (unlike some). And thanks for 
the very thorough explanation which I now follow.

R's
Graham Stow 

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#3710

Graham wrote:

> I'm a Perl veteran (well almost!) but a PHP newbie. […]
> <?php
> $formula = "!big_number - !small_number";
> ?>
> […]
> $big_number = 30000;
> $small_number = 3000;
> $formula = str_replace("!", "$", $formula);
> eval("\$formula = \"$formula\";");

You don't want a string, so don't make a string – remove the `\"'.
(I don't think Perl is so much different in that regard.)

> […]
> The above gives me...'formula = 30000 - 3000'
> when of course what I want is...'formula = 27000'

HTH

PointedEars
-- 
When all you know is jQuery, every problem looks $olvable.

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#3716

Den 07-11-2011 17:25, Graham skrev:

> <?php
> $formula = "!big_number - !small_number";
> ?>

function myFormula($big_number, $small_number) {
   return $big_number - $small_number;
}

> <?PHP
> include 'vars.php';
> $big_number = 30000;
> $small_number = 3000;
> $formula = str_replace("!", "$", $formula);
> eval("\$formula = \"$formula\";");
> //$formula = intval($formula);
> //settype($formula, "integer");
> print ("formula = $formula\n");
> ?>

include 'vars.php';
print myFormula(30000, 3000);

   Regards

     Jonathan

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