Evaluating math expressions written as strings

PHP_eval.gist

echo '<p>';


    function evaluate_everything($values, $expressions) {
        $output = [];
        foreach($expressions as $expression) {
            $row = [];
            foreach($values as $value){
                $str = '';
                eval("\$str = \"$expression\";");
                $result= eval('return '.$str.';');
                array_push($row, $result);
            }
            array_push($output, $row);
        }
        return $output;
    }


    $values = [1, 2, 3];

    $expression1 = '5*$value + 18';
    $expression2 = '10*$value - 4';
    $expression3 = '$value + 42';
    $expressions = [$expression1, $expression2, $expression3];

    $resultArray = evaluate_everything($values, $expressions);

    var_dump($resultArray);

echo '<br><br>';

$value = 5;
eval("\$value = \"$expression3\";");

$result= eval('return '.$value.';');
echo $result;

echo '<br><br>';

$string = 'cup';
$name = 'coffee';
$str = 'This is a $string with my $name in it.';
echo $str. "\n";
eval("\$str = \"$str\";");
echo $str. "\n";

echo '<p>';