$re = '/^\s*#.*$/m';
$str = '#Processed by Id: cwm.py,v 1.197 2007/12/13 15:38:39 syosi Exp
# using base http://www.prodigi.eu/instances
# Notation3 generation by
# notation3.py,v 1.200 2007/12/11 21:18:08 syosi Exp
# Base was: http://www.prodigi.eu/instances
@prefix : </ac-schema#> .
@prefix ins: </instances#> .
@prefix olanet: <http://www.ibermaticaindustria.com/soluciones/planta-mes-olanet#> .
@prefix plm: <http://hms.ifw.uni-hannover.de/#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
ins:everyone a <http://xmlns.com/foaf/0.1/Group>;
:canSee ins:public;
rdfs:member <http://127.0.0.1/OslcOlanetProvider/api/producer/01>,
#abul maal abdul muhit
[...]';
$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