What is Regular Expressions in Php

Regular Expressions

ð   The use of regular expression in PHP helps create well-designed, powerful PHP programs.

ð   The concept of regular expression is universally accepted by programmers.

ð   Programmers ignore regular expressions, which create large gap in

their programming skill.

ð   PHP based regular expressions are very simple to implement once their concept is understood.

ð   Regular expressions started out as a feature of the UNIX shell.

ð   They were designed to make it easier to find, replace and work with strings.

ð   Regular expressions have been used widely in many different parts

of UNIX based Operating System.

What is Regular Expression?

ð   A regular expression is a specially formatted pattern that can be used to find instances of one string within another.

ð   Several programming languages including Visual Basic, PERL, Java

Script and PHP support regular expressions.

ð   In another word regular expressions are basically a pattern definition language used to make complex and flexible string searches possible.

ð   Regular expressions in PHP are similar to any modern, text editor‟s

find/replace tools.

ð   This functionality makes editing a text file a whole lot easier.

ð   Regular expressions are used to check e-mail addresses, phone numbers, pin code, zip code, website URL.

ð   So programmers are not required to develop their own complex and lengthy programming routine to do above

Regular Expression Engine

ð   A Regular expressions engine is software that can process Regular expressions, like trying to match a pattern within a given string.

ð   Usually, the engine is part of a larger application and the user does not have access to the engine directly.

ð   Application will invoke the engine whenever needed making sure the right

Regular expressions is applied to the right file.

ð   Different Regular expressions engines are not fully compatible with each other.

ð   There are a few common uses of Regular expressions.

ð   Perhaps the most useful is form validation. For example, Regular expressions can be used to check that can email address entered into a

form use the correct syntax.

ð   They can also be used to complete complex search and replace operations within a given body of text.

ð   It is not possible with PHP‟s standard str_replace function.