对于Case的多个条件，Switch Statement无法正常工作

Question

$letters = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h']; 
$x = (1==1 || 2==2);
$y = (3==3 || 4==4);
$z = (5==5);

foreach ($letters as $key => $letter) {
        switch ($letter) {
            case 'a':
                echo "a";
                    break;
            case 'b':
                echo "b";
                    break;
            case 'c':
                echo "c";
                    break;
            case 'd':
                echo "d";
                    break;
            case 'e':
                echo "e";
                    break;
            case 'f':
                echo "f";
                    break;
            case 'g' && ($z || $y):
                echo "g";
                    break;
            case 'h' && ($x):
                echo "h";
                    break;
        }
}

I don't know why but at the last two cases the 'g' and 'h' It doesn't work properly and gets a double 'g', The result i expect is

abcdefgh but i keep getting abcdefgg, What am I doing wrong?

Answer 1

Given your code, the g case will always evaluate to true:

var_dump('g' && ((5==5) || (3==3 || 4==4))); // true

switch cases use loose comparison and when $letter is g it will be evaluated with true. Since g is loosley true it will execute that case:

var_dump('g' == true);  // true
var_dump('g' == false); // false

You probably need this:

        case 'g':
            if(($z || $y)) { echo "g"; }
                break;