Stacking Multiple Ternary Operators in PHP

Question

This is what I wrote :

 $Myprovince = (
($province == 6) ? \"city-1\" :
($province == 7) ? \"city-2\" :
($province == 8) ? \"city-3\" :
($province == 30) ? \         


        

Answer 1

The ternary operator is evaluated from left to right. So if you don't group the expressions properly, you will get an unexpected result.

PHP's advice is [docs]:

It is recommended that you avoid "stacking" ternary expressions. PHP's behaviour when using more than one ternary operator within a single statement is non-obvious.

Your code actually is evaluated as:

(
    (
        (
            $province == 6 ? "city-1" : $province == 7
        ) ? "city-2" : 
        $province == 8
    ) ? "city-3" : $province == 30
) ? "city-4" : "out of borders";

where it should be

$province == 6 ? "city-1" : (
    $province == 7 ? "city-2" : (
        $province == 8 ? "city-3" : (
           $province == 30 ? "city-4" : "out of borders"
        )
    )
);

This code might look fine but someone will read it and they will need more time than they should to understand what this code is doing.

---

You would be better off with something like this:

$map = array( 6 = >'city-1', 
              7 => 'city-2', 
              8 => 'city-3', 
             30 => 'city-4');

$Myprovince = "out of borders";

if(array_key_exists($province, $map)) {
    $Myprovince = $map[$province];
}

Or as @Jonah mentioned in his comment:

$Myprovince = isset($map[$province]) ? $map[$province] : 'out of borders';