$re = '/(.*?)(?:\s+v[0-9]+|\s+vol\.?\s*[0-9]+)/i';
$str = 'This is what I want v1
This is what I want Vol.27
This is what I want vol 1
This is what I want VOL. 27
';
$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