PHP: Constants

Last update on May 28 2022 12:34:11 (UTC/GMT +8 hours)

Description

A constant is an identifier for a simple value. The value cannot be modified during the script's execution. A valid constant name starts with a letter or underscore (no dollar($) sign before the name) and by convention constant identifier are always uppercase.

Constants are defined by using the define() function or by using the const keyword outside a class definition as of PHP 5.3.0. The name of the constant and the value must be placed within the parentheses. After defining it can never be changed or undefined. Only scalar data i.e. boolean, integer, float and string can be contained in constants.

PHP valid and invalid constant names

<?php
//Valid constants name
define("COUNTRY_NAME", "India");
define("CITYNAME", "New Delhi");
define("2NO_OF_STUDENTS", 60);
?>

Example of a PHP constant

<?php
define("COUNTRY_NAME", "India");
echo COUNTRY_NAME;
?>

Output :

India

View this 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