PHP_CodeSniffer is a PHP5 script that tokenises and “sniffs” PHP, JavaScript and CSS files to detect violations of a defined coding standard. It is an essential development tool that ensures your code remains clean and consistent. It can also help prevent some common semantic errors made by developers.

A coding standard in PHP_CodeSniffer is a collection of sniff files. Each sniff file checks one part of the coding standard only. Multiple coding standards can be used within PHP_CodeSniffer so that the one installation can be used across multiple projects. The default coding standard used by PHP_CodeSniffer is the PEAR coding standard.

PHP_CodeSniffer requires PHP version 5.1.2 or greater.

it can also be used to define a set of Coding Standards  for your project.