identifying repeating numbers or number patterns in php

Question

I've seen quite a few question on SO about identifying repeating patterns for crazy looking strings and stuff but nothing that will capture a repeating number or a repeating number pattern.

I'm trying to figure out a way to write a function that can identify both of these cases. For example I have a number pattern similar to 14285714285714 with the pattern being 142857-142857-14. In some cases the pattern could be say, 7575757 : 75-75-75-7. I also have a reoccurring number like 55555555 or 55555556.

How could I go about creating a function that determines if a number is either repeating or has a pattern? I guess the repeating number could be seen as a pattern in that sense. I'm kind of at a loss on this and any help on this would be greatly appreciated.

Thank you in advance.

EDIT i also only need to throw true if the pattern or re occurrence is longer than 3 digits.

UPDATE So I tried @stribizhev recommendation with preg_match and was indeed able to detect a pattern. I still need my pattern to be much more precise though. If my number is 4444 preg_match shows my pattern as 44-44. I need to be able to know the difference in 4-4-4-4 and 75-75-75. Can some one help me clarify how I would get a more precise result from the preg_match?

Here's what I have so far.

 $num = 4444;
 if (count($num) >= 3) { 
    $result = preg_match('/(\d+)\1/', $num, $matches);
    if ($result) {
       $repeat = "true";
       echo "match: ".$matches[0].", ".$matches[1]; 
    }
 }

 output: match: 4444, 44

Although this output isn't inaccurate, It's just not as specific as I need it to be. 44 is the pattern, but even more so 4 is the pattern. Just like in 7575, 75 is the pattern.

Answer 1

This pattern does the job:

$pattern = '~
    \A    # start of the string
      # find the largest pattern first in a lookahead
      # (the idea is to compare the size of trailing digits with the smallest pattern)
    (?= (\d+) \1+ (\d*) \z )
      # find the smallest pattern
    (?<pattern> \d+? ) \3+
      # that has the same or less trailing digits
    (?! .+ \2 \z)
      # capture the eventual trailing digits
    (?= (?<trailing> \d* ) )
~x';

if (preg_match($pattern, $num, $m))
    echo 'repeated part: ' . $m[0] . PHP_EOL
       . 'pattern: ' . $m['pattern'] . PHP_EOL
       . 'trailing digits: ' . $m['trailing'] . PHP_EOL;

demo