$re = '/FLAGSHARE[\S\s]*?\d\s*\d\n/';
$str = 'FLAGSHARE
xxxxxx
xxxxx, 1 2015
words....
FLAGSHARE
xxxxxx
xxxxx, 2 2015
words....
FLAGSHARE
xxxxxx
xxxxx, 3 2015
words....';
$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