I am saving operators(+,-,*) in mysql table have type varchar i have problem

PHP
1

I am saving operators(+,-,*) in mysql table have type varchar i have problem when in puting the values in formul e.g

$val1=7;
$val2=+;
$val3=5;
$val4=-;
$val5=9;

$ans=$val1.$val2.$val3.$val4.$val5;

the output is:

7+5-9

but i want to perform the action and give me the result 3

how to do?

2

I can’t think of another way to do that besides forming a valid PHP assignment as a string and using eval().

3

thanks oddz

its not working …giving parse error

4

what do you want to do with said value?

5

After you have verified that the input consists of digits, operators and parentheses only, of course :slight_smile:

6

Weird, I tried this but it didn’t work. Either I’m missing something very basic here, or… well, I must be something really basic :smiley:


<?php

$val0 = '$res=';
$val1 = 7;
$val2 = '+';
$val3 = 5;
$val4 = '-';
$val5 = 9;
$val6 = ';';

$sum = $val0 . $val1 . $val2 . $val3 . $val4 . $val5 . $val6;

echo $sum . "<br />";
eval('<?php ' . $sum . ' ?>');

var_dump(isset($res));

?>

Output:



$res=7+5-9;

boolean false

p.s. I have, of course, checked that the input consists of digits, operators and parentheses only :wink:

7

You don’t put <?php and ?> in the eval, just the code you want to evaluate.


<?php
$val0 = '$res=';
$val1 = 7;
$val2 = '+';
$val3 = 5;
$val4 = '-';
$val5 = 9;
$val6 = ';';

$sum = $val0 . $val1 . $val2 . $val3 . $val4 . $val5 . $val6;

echo $sum . "<br />";
eval($sum);

var_dump(isset($res));
var_dump($res);

/*
$res=7+5-9;
boolean true
int 3
*/

:slight_smile:

8

if the values are coming from user input you might have to do more checks, i.e.

$val0 = '$res=';
$val1 = '/'; // user supplied
$val2 = '/'; // user supplied
$val3 = ';';

eval() now throws a parse error

9

Of course, that just goes to show how often I use eval(). :smiley: