PHP Data Types : NULL

Last update on May 28 2022 12:21:33 (UTC/GMT +8 hours)

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

How to Sort Multi-dimensional Array by Value?

Try a usort, If you are still on PHP 5.2 or earlier, you'll have to define a sorting function first:

Example:

function sortByOrder($a, $b) {
    return $a['order'] - $b['order'];
}

usort($myArray, 'sortByOrder');

Starting in PHP 5.3, you can use an anonymous function:

usort($myArray, function($a, $b) {
    return $a['order'] - $b['order'];
});

And finally with PHP 7 you can use the spaceship operator:

usort($myArray, function($a, $b) {
    return $a['order'] <=> $b['order'];
});

To extend this to multi-dimensional sorting, reference the second/third sorting elements if the first is zero - best explained below. You can also use this for sorting on sub-elements.

usort($myArray, function($a, $b) {
    $retval = $a['order'] <=> $b['order'];
    if ($retval == 0) {
        $retval = $a['suborder'] <=> $b['suborder'];
        if ($retval == 0) {
            $retval = $a['details']['subsuborder'] <=> $b['details']['subsuborder'];
        }
    }
    return $retval;
});

If you need to retain key associations, use uasort() - see comparison of array sorting functions in the manual

Ref : https://bit.ly/3i77vCC