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I am trying to use regex to extract a certain syntax, in my case something like "10.100" or "20.111", in which 2 numbers are separated by dot(.) . So if I provide "a 10.100", it will extract 10.100 from the string. If I provide "a 10.100 20.101", it will extract 10.100 and 20.101.
Until now I have tried to use
preg_match('/^.*([0-9]{1,2})[^\.]([0-9]{1,4}).*$/', $message, $array);
but still no luck. Please provide any suggestion because I don't have strong regex knowledge. Thanks.

You may use
\b[0-9]{1,2}\.[0-9]{1,4}\b
See the regex demo.
Details:
\b - a leading word boundary
[0-9]{1,2} - 1 or 2 digits
\. - a dot
[0-9]{1,4} - 1 to 4 digits
\b - a trailing word boundary.
If you do not care about the whole word option, just remove \b. Also, to match just 1 or more digits, you may use + instead of the limiting quantifiers. So, perhaps
[0-9]+\.[0-9]+
will also work for you.
See a PHP demo:
$re = '/[0-9]+\.[0-9]+/';
$str = 'I am trying to use regex to extract a certain syntax, in my case something like "10.100" or "20.111", in which 2 numbers are separated by dot(.) . So if I provide "a 10.100", it will extract 10.100 from the string. If I provide "a 10.100 20.101", it will extract 10.100 and 20.101.';
preg_match_all($re, $str, $matches);
print_r($matches[0]);
Output:
Array
(
[0] => 10.100
[1] => 20.111
[2] => 10.100
[3] => 10.100
[4] => 10.100
[5] => 20.101
[6] => 10.100
[7] => 20.101
)

Regex: /\d+(?:\.\d+)/
1. \d+ for matching digits one or more.
2. (?:\.\d+) for matching digits followed by . like .1234
Try this code snippet here
<?php
ini_set('display_errors', 1);
$string='a 10.100 20.101';
preg_match_all('/\d+(?:\.\d+)/', $string, $array);
print_r($array);
Output:
Array
(
[0] => Array
(
[0] => 10.100
[1] => 20.101
)
)

$decimals = "10.5 100.50 10.250";
preg_match_all('/\b[\d]{2}\.\d+\b/', $decimals, $output);
print_r($output);
Output:
Array
(
[0] => 10.5
[1] => 10.250
)
Regex Demo | Php Demo