1. reCAPTCHA
The reCAPTCHA library allows you to create an advanced CAPTCHA system for your site that is actually used to generate validation information, even including voice verification. Of course there are recaptcha services that can be used, which provide an easy-to-use free API that is worth trying on your site.
Download reCAPTCHA | Get API Key | Document
2. Akismet
Akismet is a free service for small sites to modify the comments that the specification will add to the database (prevent malicious comments). The library has been improving.
Detailed reference Akismet Introduction
3. Services_json
JSON is a form of information delivery that humans can easily understand. But if you're not using the 5.2.0 version of PHP (PHP has the official JSON support since then), you should try this library.
View Services_json
4. Smarty
Smarty is the famous official template library. It provides a number of useful features. In fact, people who use PHP should see.
Download Smarty | Official documents
5. Pchart
Pchart is an extremely well-known data graphics library. It can provide a variety of beautiful charts for data display. In fact, people who use PHP will always encounter the use of it.
Download Pchart | Documents | View Demo
6. Simplepie
Simplepie lets you easily extract content (like RSS feeds). It can interact with multiple languages and can handle feeds in a variety of formats.
Download Simplepie | View Document | Expand Simplepie for Unique RSS Feeds
7. XML-RPC PHP Library
Sometimes you need to use XML-RPC technology to interact with other sites, so try this XML-RPC PHP library.
Download XML-RPC PHP | View Document
8. Amazon S3
Amazon's famous cloud computing platform is called "S3″." Amazon S3 Library allows you to use the cloud without any additional tools and upload a large number of data files.
Download Amazon S3 PHP Class
9. Phpmailer
Most Web applications are using the PHP mail () function. Phpmailer gives you more flexibility in handling Email, not only for any format, but also for adding attachments and customizing headers.
Download Phpmailer | View Document