PEAR
PEAR is an acronym for "PHP Extension and Application Repository", ie PHP Extension and Application repository.
PEAR to write PHP application development process commonly used functions into a library, covering the page rendering, database access, many aspects of file operations, data structures, cache operations, network protocols, WebService, users can download these libraries and appropriate make some customization to achieve the functionality they need. Avoid duplication invention "wheel." PEAR has significantly improved the development efficiency and quality PHP development program.
PECL
PECL is "PHP Extension Community Library" acronym, that PHP extensions.
PECL can be seen as an integral part of PEAR, PEAR and provides similar functionality. The difference is that all extensions are purely PEAR PHP code written in a user to download the PEAR extension can be used directly after the extended code contains PHP files to their own use. The PECL is developed using C language commonly used with PHP to add some low-level functionality difficult to complete, often the need to recompile or set in the configuration file to use in your own code.
The most direct expression: PEAR is the upper extension for PHP, PECL extension for PHP is the bottom. They are readily available to provide for specific functions or a class of applications.
Composer
Composer is a php package management tool, has the advantage that only need to provide a composer.json file, Affirming the need to use the tripartite library, a simple command will be able to depend on all of its bottles. Also easy to deploy and publish the project, because only need to provide a composer.json on the line, also provides support for automatic loading. This involves the php-fig organizations standardize the PSR-0
Summary: composer and pear function is the same, but the composer is more easy to use, pear almost been eliminated.
from：https://blog.csdn.net/wz947324/article/details/80509132