php i need null to be null, zero to be zero - php

Question

my table field status is NULL[default], or it is 0, or 1. then i assign to PHP var $status. when value is NULL i want to display no icon, when value is 0, display a gray check image, when value is 1, display a green check image.
trouble is, NULL value shows a gray check image, 0 does not show a check image. somehow NULL and 0 are alike but only in one direction. what i mean is, regardless of how i conditionally test if var is null, not null, null but not zero, they get interpreted wrongly. it is confusing. there must be a simple straight foward way to keep NULL and 0 separate and distinct. i grab the value:
$status = $Card['status']; //from above array.
if ($status == 1) {
$status = '1';
} else if ($status == 0) {
$status = '0';
} else if ($status === NULL) {
$status = 'NULL';
}
then to display the images either gray, green, or none at all i am trying this:
if ($status == '1') {
echo "<img src='../images/status_check_green.png' />";
} else if ($status == '0') {
echo "<img src='../images/porc_check_gray.png' />";
} else if ($status == 'NULL') {
echo "<img src='' />";
}
}
i know i do not need the '' around the values, but i am trying to literalize everything to force valid comparisons. likely no need for someone to try unraveling my code; but to elucidate how to keep NULL and 0 separate. it's like i am missing something fundamental here. btw, when i stuff a js var with the PHP var, it gets the correct value; they just don't follow the comparison like i need them to.
ideas?

Answer 1

HI your issue is procedure order or not type checking the 0 ( depending if you want to catch false )
if ($status == 1) {
$status = '1';
} else if ($status == 0) {
$status = '0'; //<--- this runs on null because (null == 0) is true
} else if ($status === NULL) {
$status = 'NULL'; //<--- this block is un-reachable
}
Because your not type checking with === of 0 null will return true for that condition.
See this sandbox with and example using $status = null;
http://sandbox.onlinephpfunctions.com/code/1f3dd9d83d0026aa0f682b61bed2ba858ae285aa
Outputs:
'0'
If you change it to this
if ($status == 1) {
$status = '1';
} else if ($status === 0) {
$status = '0';
} else if ($status === NULL) {
$status = 'NULL';
}
As you can see here using the same setting for $status
http://sandbox.onlinephpfunctions.com/code/d86b0c60c06338d2d6ee1c1fa9d3fa7e08a22663
Outputs
'NULL'
The other way to fix it would be to switch them so the more specific one is first.
if ($status == 1) {
$status = '1';
} else if ($status === NULL) {
$status = 'NULL';
} else if ($status == 0) { //I would prefer if(!$status){ but I'm lazy
$status = '0';
}
Then 0 would catch false as well as 0 but not null as the block above it will catch it first. You can see this last one here
http://sandbox.onlinephpfunctions.com/code/3028f5826dcede29b14dd8cfc03618ea5830c12c
Which also outputs
'NULL'
Cheers!