ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

Learn how to use PHP unset Function

Updated on October 24, 2011

Introduction

If you ever stuck in a condition where you want to free up memory by destroying any variable, group of variables or elements of array, then, you can do so by using the "unset()" function. This PHP function is a member of variable handling functions in PHP. But as per the official documentation (Notes) on PHP, this is a language construct and not a function, it cannot be called using variable functions. Some language constructs can be called without parenthesis.

List of Contents

  1. Most Common Language Constructs,
  2. Usage and Description unset Function,
  3. Syntax of Unset Function,
  4. Parameters,
  5. Practical Examples showing the usage of unset function,
  6. Resolve Your Queries.

PHP Unset Function
PHP Unset Function

Most Common Language Constructs

  1. echo(),
  2. print(),
  3. unset(),
  4. isset(),
  5. empty(),
  6. include(),
  7. require().

Usage and Description

This PHP function destroys a variable specified in it's parameter. You can destroy as many variables you want by submitting the list in comma-separated values. Well, This function does what it intends to but have some limitations related to its scope of working, Which is listed below.

  • If you'll destroy a variable inside a function using "unset" function, then, destroyed variable will not be available in rest/remaining part of function unless declared again but it'll still remain in memory i.e. outside the scope of function (If declared there previously).

Sample Example of Unset Function

<?php
function destroy_myVariable() 
{
    global $myVariable;
    unset($myVariable);
}

$myVariable = 'This is my Garbage Data';
destroy_myVariable();
echo $myVariable;

//OUTPUT OF ABOVE PHP CODE WILL BE
/*
	This is my Garbage Data
*/
?> 

Syntax

Here, below is the syntax of unset function PHP. In this syntax, "..." three dots are indicating that you can add as many parameters as argument in this function.

Synatx of unset PHP Function

void unset ( mixed $var [, mixed $... ] );

Parameters

This function does not have limit of parameters but it only accepts few kinds of values which is described below.

  • "$var" - The "php variable" or "element of any array" that needs to be destroyed.

Examples of unset Function

Here, Below are the examples showing the usage of unset function in PHP Scripts.

SImple Usage of unset function

<?php

// destroy a single variable
$myVariable="My Data";
unset($myVariable);
echo "<b>OUTPUT 1:</b> ~~~| ".$myVariable." |~~~<br />";
//Above Echo Statement Will also Issue a notice referencing to destroyed Variable

$myArray=array("one"=>"gay", "six"=>"lesbians", "three"=>"Normal Humans");

// destroy a single element of an array
unset($myArray['one']);
echo "<b>OUTPUT 2: </b>";
  print_r($myArray);
echo "<br/>";

// destroy more than one elements of array (You can use variables too)
unset($myArray['one'], $myArray['six']);
echo "<b>OUTPUT 3: </b>";
  var_dump($myArray);
echo "<br/>";

//OUTPUT OF ABOVE CODE WILL BE
/*

Notice: Undefined variable: myVariable in C:\Program Files\xampp\htdocs\online\phptest.php on line 6
OUTPUT 1: ~~~| |~~~
OUTPUT 2: Array ( [six] => lesbians [three] => Normal Humans )
OUTPUT 3: array(1) { ["three"]=> string(13) "Normal Humans" } 

*/
?> 

Ask For Help

If you have queries regarding this function or about any part of this tutorial, the, you can ask about it in comments section below. I will try my best to resolve it in a simplest way.

Comments

    0 of 8192 characters used
    Post Comment

    No comments yet.

    working

    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, hubpages.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: https://hubpages.com/privacy-policy#gdpr

    Show Details
    Necessary
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
    Features
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Marketing
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Statistics
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)