Division and Eval()

[likelylad]

I am dynamically producing a query from a table to run on another table.

The bulk of this is no problem.

The problem I am having to get 2 variables to divide.

For Example

$rowdata[$i]='$B'.$myrow["Num"].'$A'.$myrow["Num"];

Further On down in the code I use:

for($a=0;$a<$numcols;$a++){
$out="<td>rowdata[$a]</td>";
eval("\$out = \"$out\";");
echo $out;
}

This could output 1020 (i.e. 10 and 20),which is fine.

However I would like to divide these 2 numbers (i.e. 10/20).

The best I have got is to have 10/20 displayed on screen rather than the actual division result.

Hopefully the above is clear?

Does anyone have any ideas?????

 

[sleipnir214]

I don't understand. Why are you using an eval()? Why not just have the code divide one provided number by another?



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[likelylad]

The formulae is being passed as a string so the only way to get it to display the actual variable is to use eval()

 

[sleipnir214]

Your example confuses me, as $myrow['Num'] has two values in the same statement.

Here's something similar:

<?php

$a = array
(
	array ('10', '20', '/'),
	array ('10', '20', '*'),
	array ('10', '20', '-'),
	array ('10', '20', '+')
);
	
foreach ($a as $operands)
{
	$string = '$out = ' . $operands[0] . $operands[2] . $operands[1] . ';';
	
	print $string . ' : ';
	eval ($string);
	print $out;
	print '<br>';
}

On my machine it outputs:

[tt]$out = 10/20; : 0.5
$out = 10*20; : 200
$out = 10-20; : -10
$out = 10+20; : 30[/tt]



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[likelylad]

The first part of the code will produce a string like

$rowdata[1]=$Bvar1.$Avar3;
$rowdata[2]=$Bvar2.$Avar3;
$rowdata[3]=$Bvar3.$Avar3;
etc

This then needs to be evaluated in the second part of the code

 

[sleipnir214]

I think my code sample shows you how to construct evaluatable strings from parameter-driven inputs. I don't understand your last post.



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