PHP regular expression matching

Question

Given the input string "othertext ?.abc.de.fgh.i moretext" and the pattern '/\?(\.[a-zA-Z]*)*/' I'm trying to use function preg_match_all to get an array of matches with the elements .abc, .de, .fgh, and .i but only ?.abc.de.fgh.i and .i are matched. (The test)

Answer 1

You could make use of the \G anchor

(?:\?|\G(?!^))\K\.[a-zA-Z]+

In parts:

• (?: Non capture group
  • \? Match ?
  • | Or
  • \G(?!^) Assert position at the end of previous match, not at the start
• ) Close group
• \K\.[a-zA-Z]+ Forget what is currently matched, and match the . and 1+ chars a-zA-Z

Regex demo | Php demo

$re = '/(?:\?|\G(?!^))\K\.[a-zA-Z]+/';
$str = 'othertext ?.abc.de.fgh.i moretext';

preg_match_all($re, $str, $matches);
var_dump($matches[0]);

Output

array(4) {
  [0]=>
  string(4) ".abc"
  [1]=>
  string(3) ".de"
  [2]=>
  string(4) ".fgh"
  [3]=>
  string(2) ".i"
}