Search code examples
phpoperatorsevalconcatenation

Evaluate concatonated operator with numbers

I'm struggling with a small piece of code that doesn't want to evaluate itself :

$t = 5;
$s = "<=";
$r = 6;

var_dump($t.$s.$r);

Here the var_dump return "5<=6" which make sense but I just want it to tell me if 5 is inferior or equal to 6 with a boolean.

I wanted to know if there was an other way to get this boolean beside using an eval() or a switch throught all the possible operator

Thanks in advance.

Solution

  • If you want a safe and flexible solution, this allows you to define a method which is executed depending on the operator matching the key in an array, it only works with two operands, but the last one in the examples # just multiplies the first value by 4 and returns the value...

    $operators = [ "<=" => function ($a, $b) { return $a <= $b;},
    "<" => function ($a, $b) { return $a < $b;},
    ">=" => function ($a, $b) { return $a >= $b;},
    ">" => function ($a, $b) { return $a > $b;},
    "#" => function ($a) { return $a * 4; }];

$t = 5;
$s = "<=";
$r = 6;
var_dump($operators[$s]($t,$r));

$s = "<";
var_dump($operators[$s]($t,$r));

$s = ">=";
var_dump($operators[$s]($t,$r));

$s = ">";
var_dump($operators[$s]($t,$r));

$s = "#";
var_dump($operators[$s]($t,$r));

    gives...

    /home/nigel/workspace2/Test/t1.php:14:
bool(true)
/home/nigel/workspace2/Test/t1.php:17:
bool(true)
/home/nigel/workspace2/Test/t1.php:20:
bool(false)
/home/nigel/workspace2/Test/t1.php:23:
bool(false)
/home/nigel/workspace2/Test/t1.php:26:
int(20)

    It's a bit convoluted, but also extensible and safe.