The best practice for not null if statements

Question

I\'ve been writing my \"If this variable is not empty\" statements like so:

if ($var != \'\') {
// Yup
}

But I\'ve asked if this is correct, it

Answer 1

Rather than:

if (!($error == NULL))

Simply do:

if ($error)

One would think that the first is more clear, but it's actually more misleading. Here's why:

$error = null;

if (!($error == NULL)) {
    echo 'not null';
}

This works as expected. However, the next five values will have the same and (to many, unexpected) behavior:

$error = 0;
$error = array();
$error = false;
$error = '';
$error = 0.0;

The second conditional if ($error) makes it more clear that type casting is involved.

If the programmer wanted to require that the value actually be NULL, he should have used a strict comparison, i.e., if ($error !== NULL)

Answer 2

It is good to know exactly what is in your variable, especially if you are checking for uninitialized vs null or na vs true or false vs empty or 0.

Therefore, as mentioned by webbiedave, if checking for null, use

$error !== null
$error === null
is_null($error)

if checking for initilized, as shibly said

isset($var)

if checking for true or false, or 0, or empty string

$var === true
$var === 0
$var === ""

I only use empty for ''s and nulls since string functions tend to be inconsistent. If checking for empty

empty($var)
$var  // in a boolean context

// This does the same as above, but is less clear because you are 
// casting to false, which has the same values has empty, but perhaps
// may not one day.  It is also easier to search for bugs where you
// meant to use ===
$var == false

If semantically uninitialized is the same as one of the values above, then initialize the variable at the beginning to that value.

$var = ''
...  //some code

if ($var === '') blah blah.

Answer 3

There are ways:

<?php

error_reporting(E_ALL);

$foo = NULL;
var_dump(is_null($inexistent), is_null($foo));

?>

Another:

<?php

$var = '';

// This will evaluate to TRUE so the text will be printed.
if (isset($var)) {
    echo "This var is set so I will print.";
}
?>

To check if it's empty:

<?php
$var = 0;

// Evaluates to true because $var is empty
if (empty($var)) {
    echo '$var is either 0, empty, or not set at all';
}

// Evaluates as true because $var is set
if (isset($var)) {
    echo '$var is set even though it is empty';
}
?>

Answer 4

Why just don't

if (!$var)