$re = '/\b(in relation to any Facility [A-Z] Loan \[\s*(\d+%)\s*\] per cent. per annum);/m';
$str = '"Margin" means:
(a) in relation to any Facility A Loan [2% ] per cent. per annum;
(b) in relation to any Facility B Loan [ 5% ] per cent. per annum;
(c) [in relation to any Incremental Facility Loan, the percentage rate per annum specified as such in the Incremental Facility Notice relating to the Incremental Facility under which that Incremental Facility Loan is made or is to be made;]';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
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