$re = '/(?:\t|^)\d+\K,(?=\d+(?:\t|$))/mi';
$str = 'text, text bla 23,89 bla 0,5 bla
Blablabla 2325,8 869,4142 Blablabla
Blablabla 17,3 8,58 Blablabla
23,89
,
1,
,2
1,3 2,3';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php