Regex multiple pattern replacement

Question

Looking for regex expression (for php) to replace patterns multiple times without affecting remainder. The actual replace required is to reverse certain numbers, 10-1 should be changed to 1-10, i.e. "number1" "dash" "number2" where number is integer (could have more than 1 digit) should be replaced by "number2" "dash" "number1". Note that the pattern does not allow spaces. This pattern can occur any (unknown) number of times including 0.

This text can be surrounded by any other text including numbers, letters, spaces, special characters.

Examples

     asdasdasd10-1 2-3asdasd 9-2 2 3XSSADSD

should be changed to

     asdasdasd1-10 3-2asdasd 2-9 2 3XSSADSD

Similarly

     <asdasd 10 - 2 dfdsfsdfsdf 8-2

changed to

     <asdasd 10 - 2 dfdsfsdfsdf 2-8

zx81 · Accepted Answer · 2014-07-16 04:40:08Z

3

Use this:

$replaced = preg_replace('~(\d+)-(\d+)~', '\2-\1', $yourstring);

In the demo, see the substitutions at the bottom.

Explanation

The parentheses around (\d+) captures digits to Group 1
We match the -
The parentheses around (\d+) captures digits to Group 2
\2-\1 replaces with Group 2 + hyphen + Group 1

Reference

answered Jul 16, 2014 at 4:40

zx81

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6 Comments

zx81 Over a year ago

FYI: Added demo and explanation. :)

Archy Will He Over a year ago

yeah, thanks for sharing this to us :) It is a good learning tool for Regex beginners.

zx81 Over a year ago

@0ar.ch IMO the best value is in the articles in the references. :)

Archy Will He Over a year ago

Just saw them. Yup! I like the one by Rex :)

zx81 Over a year ago

@anubhava He doesn't seem to be switching them around in the 10 - 2, just the ones directly in contact like 2-3

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