$re = '/\b\d(?: ?\d){7}(?= *[,;.]|$)/m';
$str = '12345678,12345678,12345678
12345678.12345678,12345678;12345678
12345678 , 12345678 . 12345678 ; 12345678
1234 5678 .12 345678, 123 45678 ;12 3456 78';
$subst = "";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
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