Common uses of Regular expressions in php

Input validation

ð   Verifying input format, example an email address

ð   Parsing data from pre-defined variables.

ð   Searching for and replacing data(when required) in  a file or database.

ð   If PHP code space is being used to create user defined functions to validate or manipulate portions of a string, then these user-defined

functions could be fragmented and can be use regular expressions.

Types of regular expressions

ð   While the basics of regular expressions are pretty much the same across the board, there are different flavors.

ð   PHP supports two flavors of regular expressions.

ð   Perl compatible regular expressions (PCRE) and POSIX extended regular expressions have both been available since PHP3.

ð   PCRE is generally considered a bit faster, performance wise, than

POSIX.

ð   But the syntax of POSIX is easier to grasp.

ð   The basic concepts of regular expressions are the same for both types.