--- title: "PHP Filter" description: "PHP filters are used to validate and filter data coming from insecure sources, like user input. A PHP filter is used to validate and filter data comin" author: "Anonymous User" published: 2011-09-16 updated: 2019-12-04 canonical: https://www.mindstick.com/articles/732/php-filter category: "php" tags: ["php"] reading_time: 3 minutes --- # PHP Filter PHP filters are used to validate and [filter data](https://www.mindstick.com/forum/384/based-on-logged-username-to-filter-data-in-gridview) coming from insecure sources, like [user input](https://www.mindstick.com/forum/159624/setting-an-enum-from-user-input). A PHP filter is used to validate and filter data coming from insecure sources. To test, validate and filter user input or [custom data](https://www.mindstick.com/forum/160248/how-to-create-custom-data-annotations-for-custom-validation-on-model-property-in-dot-net-core) is an important part of any [web application](https://www.mindstick.com/articles/13069/progressive-web-application-pwas-all-you-need-to-know-about). The PHP filter extension is designed to make [data filtering](https://www.mindstick.com/forum/158701/how-can-implement-client-side-data-filtering-or-search-functionality-using-jquery) easier and quicker. The PHP filter extension has many of the functions needed for checking many types of user input, handled locally this provides a standard method of [filtering data](https://www.mindstick.com/forum/160900/how-to-use-searching-and-filtering-data-in-an-sql-server). You should always filter all external data.\ External data may be input data from a form, cookies data, server variables, [web service](https://www.mindstick.com/articles/45/web-services-in-asp-dot-net) data and [database query](https://www.mindstick.com/forum/159404/a-database-query-returns-a-syntaxerror) result etc. **There are three types of filters which are used in PHP, defined as follows.** 1. Validate Filters 2. Sanitize Filter 3. Other Filter ##### Validate Filters: Validate filters are used to [validate user](https://www.mindstick.com/forum/157975/how-can-use-jquery-s-form-validation-plugin-to-validate-user-input-and-provide-feedback-to-users) input value such as: integer, Boolean, float, [IP address](https://www.mindstick.com/articles/23391/why-you-should-treat-your-ip-address-like-a-closely-guarded-secret), email, URL etc. Validate filter follow the strict format rule such as email, URL etc. Let’s have an example, how to use validate filter id in PHP. ##### Example: ```                                         ``` ##### Output: ![PHP Filter](https://www.mindstick.com/mindstickarticle/eb601128-30ec-4720-9323-ba6cc25138c0/images/a720a1b0-262c-4b3e-9e9c-901cee11d1ff.png) In the same manner we can use all the validate filter id such as: FILTER_VALIDATE_INT,FILTER_VALIDATE_EMAIL, FILTER_VALIDATE_FLOAT etc. ##### Sanitize Filter: Sanitize filter are used to allow or disallow specified characters in a string. Sanitize filter have no format rule, it always return string value. Let’s have an example, how to use Sanitize filter in PHP. ##### Example: Here we have ‘SanitizeFilterPage.php’ having ‘submit’ button to submit form onto server. ```                                   
                                                                                                                                                                                                                                                                                                                                     
TO:   
From:
Subject:
                    Message Body:                                                    
                                                                       
    ``` \ ![PHP Filter](https://www.mindstick.com/mindstickarticle/eb601128-30ec-4720-9323-ba6cc25138c0/images/7fb12fe6-690a-4fd3-a438-00108dc38a94.png) When we click on ‘Submit’ button, the form is submitted to server with Get method, now we can filter URL on the ‘SanitizFilter.php’ page. ```                                         ``` ![PHP Filter](https://www.mindstick.com/mindstickarticle/eb601128-30ec-4720-9323-ba6cc25138c0/images/c81a2cb6-16ef-4d8f-92a2-107636be34d2.png) Here, we are filtering URL with ‘emailTo’ name. ##### Other Filter: ‘FILTER_CALLBACK’ is used for filter data by calling user defined function. This filter gives us full control over the data filtering. Let’s have an example, how to use FILTER_CALLBACK in PHP with user defined function. ##### Example: ```        "MyCallbackFunction"));      ?> ``` ##### Output: Here blank space (‘ ‘) is replaced by ‘ _ ‘ ![PHP Filter](https://www.mindstick.com/mindstickarticle/eb601128-30ec-4720-9323-ba6cc25138c0/images/39ce13df-ebb5-47cc-8138-915b7c8e8542.png) \ --- Original Source: https://www.mindstick.com/articles/732/php-filter Copyright © MindStick Software Pvt. Ltd. This Markdown version is provided for developers, AI systems, and offline reading.