CODEWITHSUNDEEP
phpregexpcre
mazziestar
mazziestar

Reputation: 43

Regex for substring of comma separated list

I'm a beginner to regex, so I apologize in advance if this is a naive question!

I have a string with two values separated by a comma: 12.345678,23.45678901

I am trying to use regex (this is a requirement) to return the first value with 3 decimals 12.345 and the second value with 2 decimals 23.45.

Ideally, the full regex match would be 12.345,23.45

I am able to get the first value 12.345 using the following regex: ^\d+\.\d{0,3}.

This works well because it only returns the full match (there is no Group 1 match). But I'm pretty stumped on how to get the second value 23.45 to be returned in the same string.

I've also tried this regex: (^.{0,6})(?:.*)(,)(.{0,5}), which correctly parses the first and second values, but the full match is being returned with too many decimals.

Full match: 12.345678,23.45

Group 1: 12.345

Group 2: ,

Group 3: 23.45

Any suggestions are welcome! Thank you in advance.

Upvotes: 4

Views: 339

Answers (1)

Nick
Nick

Reputation: 147146

You can use this regex to get your data:

^(\d+\.\d{3})\d*,(\d+\.\d{2})\d*$

It looks for digits followed by . and 3 decimal places (first capture group), then some number of digits followed by a comma (discarded) and then digits followed by a . and 2 decimal places (second capture group), followed finally by some number of digits and the end of string (discarded).

To use in PHP

$str = '12.345678,23.45678901';
preg_match('/^(\d+\.\d{3})\d*,(\d+\.\d{2})\d*$/', $str, $matches);
echo "first number: {$matches[1]}\nsecond number: {$matches[2]}\n";

Output:

first number: 12.345 
second number: 23.45

Demo on 3v4l.org

If you need to get both matches in the $matches[0] array (using preg_match_all), you can use this regex:

(?<=^)\d+\.\d{3}(?=\d*,)|(?<=,)\d+\.\d{2}(?=\d*$)

This regex looks for either

  • the start of string followed by some digits, a . and 3 digits (followed by some number of digits and a comma); or
  • a comma, some number of digits, a . and 2 digits (followed by some number of digits and the end of string).

To avoid capturing the unwanted data it is checked for using positive lookaheads and lookbehinds.

Demo on 3v4l.org

Upvotes: 3

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