Most newbie (and some seasoned) programmers have difficultly constructing Regular Expressions. Many a times one needs to create a Regexp quickly to test a a particular piece of code. However, not being comfortable withe Regexps can be a problem. VerbalExpressions is a PHP library that enables you to construct regular expressions using natural language like constructs. Think of it like a DSL for building Regexps.



Below is a sample PHP code that constructs a regular expression which tests whether a given string is a valid url.

startOfLine() ->then("http") ->maybe("s") ->then("://") ->maybe("www.") ->anythingBut(" ") ->endOfLine(); if($regex->test("http://www.codediesel.com")) echo "valid url"; else echo "invalid url"; ?>

The main part of the code the DSL like interface that helps you build a Regexp.

$regex ->startOfLine() ->then("http") ->maybe("s") ->then("://") ->maybe("www.") ->anythingBut(" ") ->endOfLine();

If you want to see what regular expression the code has built, we can use the getRegex function of the class.

startOfLine() ->then("http") ->maybe("s") ->then("://") ->maybe("www.") ->anythingBut(" ") ->endOfLine(); echo $regex->getRegex();

This will print the Regexp given below.

/^(http)(s)?(\:\/\/)(www\.)?([^ ]*)$/m

We can now use the above Regexp in our code to accomplish the same thing as above.

$myRegexp = '/^(http)(s)?(\:\/\/)(www\.)?([^ ]*)$/m'; if (preg_match($myRegexp, 'http://www.codediesel.com')) { echo 'valid url'; } else { echo 'invalud url'; }

We can also use the $regex object given in the above example directly in our code where the particular Regexp is required.

include_once('VerbalExpressions.php'); $regex = new VerEx; $regex ->startOfLine() ->then("http") ->maybe("s") ->then("://") ->maybe("www.") ->anythingBut(" ") ->endOfLine(); if (preg_match($regex, 'http://www.codediesel.com')) { echo 'valid url'; } else { echo 'invalud url'; }

The PHP version of VerbalExpressions is a port of the original JavaScript version, JSVerbalExpressions. Additional modifiers that will help you build regular expressions can be found here.