CODEWITHSUNDEEP
phpternary-operator
piagetblix
piagetblix

Reputation: 109

Understanding ternary false

The ternary false seems to have no relevance. How is it working in this example?

PHP beginner here, I have a little program that was asking for a base number and returning a cubed result. I initially wrote it with an if/else but would get “unnamed index” errors, but that was resolved by using isset(). Next issue was "A non-numeric value” for the variable passed to the pow(). I got input to use the ternary below and it now works. 


    <?php

    $base = (int) (isset($_POST['base']) ? $_POST['base'] : 0); 

    if ($base) {
        echo number_format(pow($base, 3));
    }
    else {
        echo 'Please enter a number';
    }

    ?>

I’m looking for an explanation of how the false after the : is working. It doesn’t seem to matter what is there - string, int etc. I first assumed that by having 0 it was passing false to the if/else below and therefore echoing the else statement.

To follow up, I found that simply using the (is_numeric(($_POST['base']))) as suggested by @Mark Locklear in the if statement was what I was originally looking for. Going down the ternary path lead me astray, but was definitely a learning experience. Therefore the How to write a PHP ternary operator will not fully solve my original problem. Thanks

Upvotes: 0

Views: 203

Answers (2)

Jonathan Eltgroth
Jonathan Eltgroth

Reputation: 839

PHP is loosely typed. What that basically means that any variable can change its type at any time. You could have $base = 'zero'; which would imply it's a string, and then on the next line have $base = 0;, and PHP won't care.

You're correct in a sense that 0 is equivalent to false, and that PHP will resolve it as false, but strictly speaking 0 is an integer. If you want to flag a condition as a boolean false, to make your code clear, you should just use false instead of 0.

When dealing with If conditionals, false, 0, null, and '' will all resolve as false.

Upvotes: 0

Paolo
Paolo

Reputation: 15827

First

(isset($_POST['base']) ? $_POST['base'] : 0)

evaluates to $_POST['base'] if the key base exists, 0 otherwise

Then...

$base = (int) (isset($_POST['base']) ? $_POST['base'] : 0);

...casts the result to int.

If the user enters a non numeric string (ex. ABC) or passes an empty string then $base is set to 0

Finally

if ($base) {

casts $base to boolean. Any number different from 0 is evaluated as true. 0 is evaluated as false and leads to execution of the else block.

Any input numeric and different from 0 will be cubed.

No input, a non numeric string or the value 0 will lead to Please enter a number

Upvotes: 1

Related Questions