php switch statement error on int = 0

Question

I am having a problem in php switch case.

When i set $number=0 it should run very first case but here this code returns 10-20K that is in second case.

I checked comparison operators, tested them in if else case they return correct values but here first case do not run on $number=0

Why is this happening ? php consider 0 as false or something wrong in code ?

Link to codepad paste http://codepad.org/2glDh39K

also here is the code

<?php

$number = 0;

    switch ($number) {
     case ($number <= 10000):
            echo "0-10K";
           break;
        case ($number > 10000 && $number <= 20000):
            echo "10-20K";
            break;
        case ($number > 20000 && $number <= 30000):
            echo "20-30K";
            break;
        case ($number > 30000 && $number <= 40000):
            echo "30-40K";
            break;
        case ($number > 40000 && $number <= 50000):
            echo "40-50K";
            break;
        case ($number > 50000 && $number <= 60000):
            echo "50-60K";
            break;
        case ($number > 60000 && $number <= 70000):
            echo "60-70K";
            break;
        case ($number > 70000 && $number <= 80000):
            echo "70-80K";
            break;
        case ($number > 80000 && $number <= 90000):
            echo "80-90K";
            break;
        case ($number > 90000):
            echo "90K+";
            break;

        default: //default
            echo "N/A";
            break;
}

?>

Answer 1

You are almost using the switch in reverse, but not quite. You need to either go fully into reverse by writing switch(true):

switch (true) { // IMPORTANT CHANGE HERE!
    case ($number <= 10000):
        echo "0-10K";
       break;
    case ($number > 10000 && $number <= 20000):
        echo "10-20K";
        break;
    // etc
}

or otherwise change the whole thing to if/else:

if ($number <= 10000) {
    echo "0-10K";
else if ($number > 10000 && $number <= 20000) {
    echo "10-20K";
}
// etc

Two important notes:

1. Reverse switch usually looks terribly counter-intuitive the first time you see it. Please do not use it if you don't feel comfortable with it.
2. Your conditionals could be simplified -- assuming they appear in order, each $number > X part is made redundant by the fact that the check in the previous conditional ($number <= X) has already failed. However, it can be argued that keeping the checks makes the code more robust in the face of modification.

Answer 2

switch ($number) {
 case ($number <= 10000):   // check $number == ($number <= 10000)
       echo "0-10K";
       break;
 // you hit the below because `0 == false` is true in php
 case ($number > 10000 && $number <= 20000): // check $number == ($number > 10000 && $number <= 20000)
        echo "10-20K";
        break;
 // ...

But you could do it with less code:

function showRange($number) {
    if ($number > 90000) {
       echo "90K+";
       return;
    }
    echo sprintf("%s-%sK", (int) ($number / 10000) * 10, ((int) ($number / 10000) +1) * 10 );
}