Summary

PHP supports two implementations of regular expressions—POSIX and PCRE. PCREs support more character classes and special features such as nongreedy matching and look-arounds.

Regular expressions allow you to do much more than simple searching and replacing within strings. Using regular expressions in PHP, you can find strings according to specific rules, validate user input, process files such as CSV and tab-delimited files, and make complicated replacements in text. Combined with the other capabilities in PHP, the possibilities are nearly endless.

For more about using regular expressions, see Regular Expression Recipes: A Problem-Solution Approach (Apress, 2005) and Regular Expression Recipes for Windows Developers: A Problem-Solution Approach (Apress, 2005).