- preg_replace: documentation ( source)
<?php
$str = "A N K U N F T 11.08.15\r
*** NEUBUCHUNG ***\r
11.08.15 xxx xxx X3 2830 14:25 17:50\r
18.08.15 xxx xxx X3 2831 18:40\r
F882129 dsdsaidsaia\r
F882129 xxxyxyagydaysd\r
\r
\r
A N K U N F T 18.08.15\r
*** NEUBUCHUNG ***\r
11.08.15 xxx xxx X3 2830 14:25 17:50\r
18.08.15 xxx xxx X3 2831 18:40\r
F881554 ZXCXZCXCXZCCXZ\r
F881554 xcvcxvcxvcvxc\r
F881554 xvcxvcxcvxxvccvxxcv\r
\r
\r
11.08.15 xxx xxx X3 2830 14:25 17:50\r
18.08.15 xxx xxx X3 2831 18:40\r
F881605 xczxcdfsfdsdfs\r
F881605 zxccxzxzdffdsfds ";
$re = "/(?:\sF\d+.*?\r\n\r\n)(\r\n)/";
$subst = ">>CUT HERE>>";
$result = preg_replace($re, $subst, $str);
echo $result;
?>