switch statement will not equate zero? - php

Question

I have the following function that works properly, except for when you use the input value of 0. I tried searching around to see if the 0 is equated as a NULL or if I'm doing something wrong.
When a zero is input, it outputs advanced which is greater than 20. Can anyone explain? Thanks
I plan on making the switch equate 0-10, 11-20, 21-30, 31-40, 41+ but for this example i am just using two scenarios. Thanks
**EDIT I do want values when its 20 :)
function strengthPlan( $data ) {
$data = ( int ) $data;
switch( $data ) {
case( $data <= 19 ):
$result = 'standard strength';
break;
case( $data >= 20 ):
$result = 'advanced strength';
break;
}
return $result;
}
echo strengthPlan( 0 );

Answer 1

Your logic is incorrect. Switch statements are checking for equality. Your code is checking whether $data is equal to TRUE or FALSE.
case( $data < 20 ):
will evaluate to:
case( TRUE ):
because 0 < 20.
Since 0 is not equal to TRUE but to FALSE (after conversion), the second case is run.
Basically, you cannot use switch case for < or > but only for ==.

Answer 2

That's not how switch statements. They compare the case to the value you provide to switch. Here's what you should do instead:
function strengthPlan($length) {
return $length >= 20 ? 'advanced strength' : 'standard strength';
}
If you're planning on using more conditions, then use an if...elseif statement as follows:
function strengthPlan($length) {
if ($length < 5) return 'micro strength';
elseif ($length < 10) return 'tiny strength';
elseif ($length < 15) return 'small strength';
elseif ($length < 20) return 'standard strength';
elseif ($length < 30) return 'advanced strength';
else return 'super strength!!!!!';
}
It will trickle down each condition until it hits a number that it is within. Alternatively, you can use sort of a lookup table style like this:
function strengthPlan($length) {
$plans = array(
1 => 'super strength!!!!!',
$length < 30 => 'advanced strength',
$length < 20 => 'standard strength',
$length < 15 => 'small strength',
$length < 10 => 'tiny strength',
$length < 5 => 'micro strength',
);
return $plans[1];
}
There was a discussion about this here: http://forums.devnetwork.net/viewtopic.php?f=50&t=113253

Answer 3

Using switch in this case is wrong
Use this one
http://sandbox.phpcode.eu/g/b4053.php
<?php
function strengthPlan( $data ) {
return ($data > 20) ? 'advanced strenght' : 'standard strenght';
}
echo strengthPlan( 0 );