Extract numbers after each occurrence of a substring [closed]

My input:

$string = " text1 .id.123 .id.4576 text4 .id.56778 text 5 .id.76728";

How can I get output with php?

Extract number after .id.

Desired result:

123,4576,56778,76728

Answer

Match a literal dot, then id, then a literal dot, then reset the fullstring match with K, then match one or more digits.

Implode the matches with commas.

Code: (Demo)

$string = " text1 .id.123 .id.4576 text4 .id.56778 text 5 .id.76728";
preg_match_all('~.id.Kd+~', $string, $m);

echo implode(',', $m[0]);
// 123,4576,56778,76728