Removing Duplicate Elements from an Array in PHP
By: David Sklar in PHP Tutorials on 2008-12-01
You want to eliminate duplicates from an array.
If the array is already complete, use array_unique(), which returns a new array that contains no duplicate values:
$unique = array_unique($array);
If you create the array while processing results, here is a technique for numerical arrays:
foreach ($_REQUEST['fruits'] as $fruit) {
if (!in_array($array, $fruit)) { $array[ ] = $fruit; }
}
Here's one for associative arrays:
foreach ($_REQUEST['fruits'] as $fruit) {
$array[$fruit] = $fruit;
}
Once processing is completed, array_unique()is the best way to eliminate duplicates. But, if you're inside a loop, you can eliminate the duplicate entries from appearing by checking if they're already in the array.
An even faster method than using in_array()is to create a hybrid array in which the key and the value for each element are the same. This eliminates the linear check of in_array() but still allows you to take advantage of the array family of functions that operate over the values of an array instead of the keys.
In fact, it's faster to use the associative array method and then call array_values()on the result (or, for that matter, array_keys( ), but array_values() is slightly faster) than to create a numeric array directly with the overhead of in_array().
Add Comment
This policy contains information about your privacy. By posting, you are declaring that you understand this policy:
- Your name, rating, website address, town, country, state and comment will be publicly displayed if entered.
- Aside from the data entered into these form fields, other stored data about your comment will include:
- Your IP address (not displayed)
- The time/date of your submission (displayed)
- Your email address will not be shared. It is collected for only two reasons:
- Administrative purposes, should a need to contact you arise.
- To inform you of new comments, should you subscribe to receive notifications.
- A cookie may be set on your computer. This is used to remember your inputs. It will expire by itself.
This policy is subject to change at any time and without notice.
These terms and conditions contain rules about posting comments. By submitting a comment, you are declaring that you agree with these rules:
- Although the administrator will attempt to moderate comments, it is impossible for every comment to have been moderated at any given time.
- You acknowledge that all comments express the views and opinions of the original author and not those of the administrator.
- You agree not to post any material which is knowingly false, obscene, hateful, threatening, harassing or invasive of a person's privacy.
- The administrator has the right to edit, move or remove any comment for any reason and without notice.
Failure to comply with these rules may result in being banned from submitting further comments.
These terms and conditions are subject to change at any time and without notice.
- Data Science
- Android
- React Native
- AJAX
- ASP.net
- C
- C++
- C#
- Cocoa
- Cloud Computing
- HTML5
- Java
- Javascript
- JSF
- JSP
- J2ME
- Java Beans
- EJB
- JDBC
- Linux
- Mac OS X
- iPhone
- MySQL
- Office 365
- Perl
- PHP
- Python
- Ruby
- VB.net
- Hibernate
- Struts
- SAP
- Trends
- Tech Reviews
- WebServices
- XML
- Certification
- Interview
categories
Related Tutorials
Send push notifications using Expo tokens in PHP
PHP convert string to lower case
A Basic Example using PHP in AWS (Amazon Web Services)
Different versions of PHP - History and evolution of PHP
PHP code to write to a CSV file for Microsoft Applications
PHP code to write to a CSV file from MySQL query
PHP code to import from CSV file to MySQL
Password must include both numeric and alphabetic characters - Magento
Resume or Pause File Uploads in PHP
PHP file upload prompts authentication for anonymous users
PHP file upload with IIS on windows XP/2000 etc
Comments