$re = '/\S+\[v=\"(timeSeries)-(\w+)\",g=\"(\w+)\",p=\"(\S+)\"\]\S+array\[(\d+)\]\/(\S+)/';
$str = 'root/12-825-ReturnAndStatsCompositeAPI[v="timeSeries-return",g="timeSeries",p="{"rollingPeriod":"1Y","numberOfPeriods":"5","asOfDate":"2016-12-31","startDate":"2011-12-31","frequency":"1Y"}"]/data/share_classes/array[1]/returns_series/returns/array[1]/net/cumulative
root/2-825-ReturnAndStatsCompositeAPI[v="timeSeries-benchmark",g="timeSeries",p="{"rollingPeriod":"1Y","column":"column","numberOfPeriods":"5","asOfDate":"2016-12-31","startDate":"2011-12-31","frequency":"1Y"}"]/data/share_classes/array[1]/benchmark_types/benchmark_types_breakdown/array[3]/returns_series/returns/array[1]/gross/annualized
root/2-825-ReturnAndStatsCompositeAPI[v="timeSeries-benchmark",g="timeSeries",p="{"rollingPeriod":"1Y","column":"column","numberOfPeriods":"5","asOfDate":"2016-12-31","startDate":"2011-12-31","frequency":"1Y"}"]/data/share_classes/array[1]/benchmark_types/benchmark_types_breakdown/array[3]/mpt_statistics_series/relative/gross/array[1]/excess_return
';
preg_match_all($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