How do get around 0 being treated as a null value?

[Twey]

That would make some sense, but it seems it should trigger an error or at least a warning, rather than just ignoring the whole statement.

[CrazyChop]

That would make some sense, but it seems it should trigger an error or at least a warning, rather than just ignoring the whole statement.

By default, PHP is rather lenient. If it comes across a variable not declared before and is being used, it will create it on the spot. To catch those errors, put this at the start of any PHP script

error_reporting(E_ALL); 

In fact, this is my SOP. Helps to catch a lot of bugs due to mis-spelling and such.

[Twey]

I was not using any variables, and I had turned on E_ALL error-reporting (as you can see from the transcript of the session I posted). I agree that it is usually a good idea to turn on E_ALL in new scripts.

[JasonDFR]

You have to feed empty() a variable. Constants cause parse errors. I don't know why you weren't getting errors Twey.

php > echo empty(0) ? 'yes' : 'no';

Parse error: syntax error, unexpected T_LNUMBER, expecting T_STRING or T_VARIABLE or '$' in php shell code on line 1
php > print empty(0) ? 'yes' : 'no';

Parse error: syntax error, unexpected T_LNUMBER, expecting T_STRING or T_VARIABLE or '$' in php shell code on line 1
php > $var = 0;

php > print empty($var) ? 'yes' : 'no';
yes
php > 

My recommendation for the OP is:

if ( $_POST['description'] == '' || !is_numeric($_POST['id']) ) {
    die('You did not complete all of the required fields');
} 

[Twey]

is_numeric() is good, but I stand by my recommendation of === for the former.

[JasonDFR]

$_POST['description'] = '';
$_POST['id'] = 100;

if ( $_POST['description'] === NULL || !is_numeric($_POST['id']) ) {
    die('You did not complete all of the required fields');
} 

The problem with === NULL is that it doesn't test for an empty string. If the POST variable is set, which if the form was submitted, it will be, NULL won't filter anything.

[Schmoopy]

I think he was in favour of:

if ( $_POST['description'] === '' || !is_numeric($_POST['id']) ) {
    die('You did not complete all of the required fields');
} 

Not:

if ( $_POST['description'] === NULL || !is_numeric($_POST['id']) ) {
    die('You did not complete all of the required fields');
} 

[JasonDFR]

I think he was in favour of:

if ( $_POST['description'] === '' || !is_numeric($_POST['id']) ) {
    die('You did not complete all of the required fields');
} 

Not:

if ( $_POST['description'] === NULL || !is_numeric($_POST['id']) ) {
    die('You did not complete all of the required fields');
} 

Oh. Ok.

What is the difference between =='' and ===''. Is 0 =='' true, whereas 0 ==='' not true? In the case of posted variables which I think are always going to be strings, why does === make a difference?

[Twey]

Well, for example, '0' == false. Strings can be coerced too.

[JasonDFR]

I'm sorry Twey, please bare with me.

I am not seeing a difference:

<?php

$_POST['description'] = '0';
$_POST['id'] = 100;

// BETWEEN

if ( $_POST['description'] === '' || !is_numeric($_POST['id']) ) {
    die('You did not complete all of the required fields');
}

// AND

if ( $_POST['description'] == '' || !is_numeric($_POST['id']) ) {
    die('You did not complete all of the required fields');
}

exit;

What am I missing? Or is it that you are saying since we know the $_POST variable is a string we should explicitly test for the value and type, hence === '' , where '' is an empty string ?