Online PHP editor | output for cttXo

<?php define('CALCULATION_REGEXP_STRUCTURED_REFERENCE', '([\p{L}_\\\\][\p{L}\p{N}\._]+)?(\[(?>[^\[\]]|(?R))+\])'); $formula = '=SUM(Sales_Data[[#This Row],[Q1]:[Q4]])'; $offset = 5; // This works // No start anchor, but using the preg_match() $offset argument to specify the start point for the search preg_match('/' . CALCULATION_REGEXP_STRUCTURED_REFERENCE . '/misu', $formula, $matches, 0, $offset); var_dump($matches); // This doesn't work // Creating a substring for the part of the formula that we want to search $partialFormula = substr($formula, $offset); var_dump($partialFormula); // and using the start anchor in our regexp preg_match('/^' . CALCULATION_REGEXP_STRUCTURED_REFERENCE . '/misu', $partialFormula, $matches); var_dump($matches);