Question

Suppose you have some strings, how should I transform them in order to be able to use logical operations on them in PHP? Is it even possible?

Example: I want

"x=1"&&"x=0"

to return false.

Answer 1

Introduction

I noticed you have both Logical Operator && and Assignment Operator in a string = and you want to evaluate the assignment has a logical operator in a string. Seriously i don’t know how you got here but this is very wrong but for education purpose tag along

Breakdown

"x=1"  &&  "x=0" = False 
  ^    ^     ^
  |    |     | 
       |     |
X == 1 |     |
       |     |
      AND    |
             |
           X == 0

The above expression would always be false because X can not be equal to 0 and 1 at the same time

To be able to have such evaluation in PHP you need to write your own function eg logicalString where you can evaluate the expression with something like logicalString("x=1") or logicalString("x=0")

Assumption

$x = 1; // Imagine value of X 

Example 1 &&

// Start Evaluation with &&
if (logicalString("x=1") && logicalString("x=0")) {
    echo "&& - True\n";
} else {
    echo "&& - False\n";
}

Output 1

&& - False 

Example 2 – ||

// Start Evaluation with ||
if (logicalString("x=1") || logicalString("x=0")) {
    echo "|| - True\n";
} else {
    echo "|| - False\n";
}

Output 2

|| - True

Function Used ( Not to be used in production See Why )

function logicalString($str) {
    parse_str($str, $v);
    foreach ( $v as $k => $var ) {
        if (! isset($GLOBALS[$k]) || $GLOBALS[$k] != $var)
            return false;
    }
    return true;
}

SEE ONLINE DEMO on PHP 4.3.0 – 5.5.0alpha3