$re = '/({.*?})|#.*/m';
$str = ' This is 1. # Comment 1.
This is 2. # Comment 2
#Comment 3 {#Commit4}
This is 3.
# Commit5
This is 4.{#This is 5} # Commit6
#Commit7
This is 6.
# Commit8 #Commit9
#Commit10
# Commit11
#Commit12 #Commit13
{ # This is 7}; { # This is 8 } # Commit14
{# This is 9}; { # This is 10 }={# This is 11} {# This is 12}={# This is 13}# Commit15
# Commit16 {# Commit17 }';
$subst = "\1";
$result = preg_replace($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