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PHP Data Types : NULL

Description

The special NULL value represents a variable has no value (nonvalue or unvalue). It is similar to Python's" None" or Perl's "undef".

NULL is the only possible value of type NULL.

It identifies variables being empty or not and useful to differentiate between the empty string and null values of databases.

There is only one value of type NULL, and that is the case-insensitive keyword NULL.

The following is an example of using NULL.

Syntax to define php null type

<?php
$value = NULL;
?>

In the following example, $var set to NULL and using var_dump and is_null it is shwon that the value of $var is NULL.

Example :

<?php
$var = NULL;
var_dump(is_null($var));
?>

Output :

bool(true)

View the example in browser

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PHP: Tips of the Day

PHP: How to convert string to boolean?

Strings always evaluate to boolean true unless they have a value that's considered "empty" by PHP (taken from the documentation for empty):

  1. "" (an empty string);
  2. "0" (0 as a string)

If you need to set a boolean based on the text value of a string, then you'll need to check for the presence or otherwise of that value.

$test_mode_mail = $string === 'true'? true: false;

EDIT: the above code is intended for clarity of understanding. In actual use the following code may be more appropriate:

$test_mode_mail = ($string === 'true');

or maybe use of the filter_var function may cover more boolean values:

filter_var($string, FILTER_VALIDATE_BOOLEAN);

filter_var covers a whole range of values, including the truthy values "true", "1", "yes" and "on".

Ref : https://bit.ly/33SQ3eP