CodeIgniter is a powerful PHP framework with a very small footprint, built for PHP coders who need a simple and elegant toolkit to create full-featured web applications. If you're a developer who lives in the real world of shared hosting accounts and clients with deadlines, and if you're tired of ponderously large and thoroughly undocumented frameworks.

CodeIgniter is right for you if:

  • You want a framework with a small footprint
  • You need exceptional performance
  • You need broad compatibility with standard hosting accounts that run a variety of PHP versions and configurations
  • You want a framework that requires nearly zero configuration
  • You want a framework that does not require you to use the command line
  • You want a framework that does not require you to adhere to restrictive coding rules
  • You are not interested in large-scale monolithic libraries like PEAR
  • You do not want to be forced to learn a templating language (although a template parser is optionally available if you desire one)
  • You eschew complexity, favoring simple solutions
  • You need clear, thorough documentation

Source: CodeIgniter