Description:
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In certain cases, when using \K escape sequence (reset beginning of reported match) with preg_replace, result is not as expected. Every other match seems to be skipped.

The test-pattern (?: |\G)\d\B\K is to separate digits of numbers preceded by start or space with *. This pattern works as expected e.g. in regex101 pcre-mode: https://regex101.com/r/gF7uB7/1 but not with preg_replace (at least with PHP 5.5.14) where it seems to skip every other zero-width match: https://eval.in/415050


Test script:
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<?

$pattern = '~(?: |\G)\d\B\K~';

$replace = "*";

$str = "123 a123 1234567 b123";

echo preg_replace($pattern, $replace, $str);

?>

Expected result:
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1*2*3 a123 1*2*3*4*5*6*7 b123

Actual result:
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1*23 a123 1*23*45*67 b123