Solved

RegEx search for repeating hyphens

Posted on 2011-02-20
4
653 Views
Last Modified: 2012-05-11
I am trying to replace multiple hyphens with a single one. Here is my php code to achive this

<?php
  $string = "a--b---c-d-e";
  $newstring = preg_replace("/(-)(\1+)/", "-", $string);
?>

Open in new window


I want the $newsting to be "a-b-c-d-e"

However, it does not do anything to the original string. Why is it not working?
0
Comment
Question by:hvs69
4 Comments
 
LVL 27

Accepted Solution

by:
Lukasz Chmielewski earned 125 total points
Comment Utility
Try
<?php
  $string = "a--b---c-d-e";
  $newstring = preg_replace("/[-]+/", "-", $string);
  echo"$newstring";
?>
0
 
LVL 4

Expert Comment

by:LAMASE
Comment Utility
i agree with @Roads. If you want something more general you can use

<?php
  $string = "a--b--  ## -c-d-..e(@)-g";
  $newstring = preg_replace("/[^a-z]+/", "-", $string);
  echo $newstring;
?>

this will eliminate everything between lowercase letters and puts a single hypen between..

This and @Roads solutions doesn't remove the trailing hypens: if you have

$string = '-a-b-';

it will keep as is. Do you need this too? You can do it in two easy steps (or in one with a more complex regexp)

<?php
  $string = "a--b---c-d-e";
  $newstring = preg_replace("/[^a-z]+/", " ", $string);
  $newstring = preg_replace("/ +/", "-", trim($string));
  echo"$newstring";
?>

0
 
LVL 1

Expert Comment

by:jfk013097
Comment Utility
ereg_replace("--*", "-", $string)

will replace all multiple instances of - with a single one
0
 
LVL 108

Expert Comment

by:Ray Paseur
Comment Utility
ereg functions are deprecated.

Regarding this, "it does not do anything to the original string." - that is correct, because the new value is assigned to the variable named $newstring.

http://www.laprbass.com/RAY_temp_hvs69.php

Outputs: a-b-c-d-e
<?php // RAY_temp_hvs69.php
error_reporting(E_ALL);

// TEST DATA FROM THE POST AT EE
$string = "a--b---c-d-e";

// CONSTRUCT A REGEX
$regex 
= '/'  // REGEX DELIMITER
. '-+' // MORE THAN ONE HYPHEN
. '/'  // REGEX DELIMITER
;

// REPLACE THE HYPHENS WITH ONE HYPHEN
$newstring = preg_replace($regex, '-', $string);
echo $newstring;

Open in new window

0

Featured Post

Free Trending Threat Insights Every Day

Enhance your security with threat intelligence from the web. Get trending threat insights on hackers, exploits, and suspicious IP addresses delivered to your inbox with our free Cyber Daily.

Join & Write a Comment

Whatever be the reason, if you are working on web development side,  you will need day-today validation codes like email validation, date validation , IP address validation, phone validation on any of the edit page or say at the time of registration…
Developers of all skill levels should learn to use current best practices when developing websites. However many developers, new and old, fall into the trap of using deprecated features because this is what so many tutorials and books tell them to u…
Learn how to match and substitute tagged data using PHP regular expressions. Demonstrated on Windows 7, but also applies to other operating systems. Demonstrated technique applies to PHP (all versions) and Firefox, but very similar techniques will w…
Explain concepts important to validation of email addresses with regular expressions. Applies to most languages/tools that uses regular expressions. Consider email address RFCs: Look at HTML5 form input element (with type=email) regex pattern: T…

763 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

8 Experts available now in Live!

Get 1:1 Help Now