CODEWITHSUNDEEP
phpregex
Placido
Placido

Reputation: 1385

RegEx replace with condition: separate adjacent numbers only

I have a txt file with numbers:

1-2 c., 3-6 c., 7-8 c., 12-15 c. etc.

I need to separate adjacent numbers (1-2 and 7-8 in the example) with " and " while the rest of the numbers I want to leave as they are, so that I get this:

1 and 2 c., 3-6 c., 7 and 8 c., 12-15 c. etc.

If I wanted to replace all of the hyphens I could do that like this: 

$newtxt = preg_replace('#(\d+)-(\d+)#', '$1 and $2', $txt);

I can do it easily with other means of PHP, but the problem is that I need to do that with the help of regular expressions only. Is that possible?

Upvotes: 0

Views: 200

Answers (2)

Borodin
Borodin

Reputation: 126742

You need preg_replace_callback which will allow you to write a function that returns the required replacement string depending on the matched and captured strings.

$str = '1-2 c., 3-6 c., 7-8 c., 12-15 c. etc. ';

$str = preg_replace_callback(
  '/(\d+)-(\d+)/',
  function($match) {
    return $match[2] == $match[1] + 1 ? "$match[1] and $match[2]" : $match[0];
  },
  $str
);

echo $str;

output

1 and 2 c., 3-6 c., 7 and 8 c., 12-15 c. etc.

Upvotes: 0

Ateszki
Ateszki

Reputation: 2253

You can use preg_replace_callback and use the function. It is not fully regexp but close to it.

function myCallback ($match){
   if($match[1] == $match[2]-1){
       return $match[1]." and ".$match[2];
   } else {
       return $match[0];
   }
}
preg_replace_callback(
    '#(\d+)-(\d+)#',"myCallback",$txt
);

Hope it helps.

Upvotes: 1

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