# Migrating from PHP 5.1.x to PHP 5.2.x

## Table of Contents

- What has changed in PHP 5.2.x
- Backward Incompatible Changes
- New Error Messages
- Changes in PHP datetime support
- New Parameters
- New Functions
- New Methods
- Removed Extensions
- New Extensions
- New Classes
- New Global Constants
- New Class Constants
- New INI Configuration Directives
- Error Reporting
- Other Enhancements

See also the migration guides for PHP versions 5.0.x, 5.1.x, 5.3.x, 5.4.x, 5.5.x and 5.6.x.