PHP - Best way to parse array of conditions

Question

I have a PHP array like so:

$booleans = array(true, '||', false, '&&', true, '||', false);

Now I would now like to convert this array to a condition, e.g.:

if(true || false && true || false){

     // Do something

}
else{

    // Do something else

}

Preferably, for security reasons, I want to avoid using eval.

Is this possible? If so, what is the most efficient way to do it?

Answer 1

This is not a finite solution for all operations and precedence, but a direction on how you may resolve it. You can refer to Shunting yard algorithm .

$validateExpression = function (array $expression): bool {
    $allowedOperators = ['&&', '||'];
    $values = [];
    $operators = [];
    foreach ($expression as $expr) {
        if (is_bool($expr)) {
            $values[] = $expr;
            continue;
        }
        if (in_array($expr, $allowedOperators)) {
            $operators[] = $expr;
            continue;
        }
        throw new \InvalidArgumentException('Invalid expression');
    }

    while($operators) {
        $a = array_shift($values);
        $b = array_shift($operators);
        $c = array_shift($values);
        array_unshift($values, match($b) {
            '&&' => $a && $c,
            '||' => $a || $c,
        });
    }

    return reset($values);
};

var_dump($validateExpression([true, '||', false, '&&', true, '||', false]));
var_dump(true || false && true || false);

Output

bool(true)
bool(true)