$re = '/(?:[\d]{2,3}?(?::IF))?[\s,&]+(?:with)?|(\S+)/m';
$str = '01:IF rd.h && dq.L && o.LL && v.L THEN la.VHB , av.VHR with 0.4610;';
$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