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RegEx search for repeating hyphens

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);
?>

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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?

ASKER CERTIFIED SOLUTION

Lukasz Chmielewski

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LAMASE

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";
?>

jfk013097

ereg_replace("--*", "-", $string)

will replace all multiple instances of - with a single one

Ray Paseur

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;

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