$re = '/(?:(?=(?&V_Obj)){(?:(?&V_KeyVal)(?&Sep_Obj))*?\s*"category"\s*:\s*\[\s*|(?!^)\G(?&Sep_Ary)\s*)(?:\s*(?&V_Value)(?&Sep_Ary))*?\K(?:(?&Numb)|(?&Str)|true|false|null)(?(DEFINE)(?<Sep_Ary>\s*(?:,(?!\s*[}\]])|(?=\])))(?<Sep_Obj>\s*(?:,(?!\s*[}\]])|(?=})))(?<Str>(?>"[^\\\\"]*(?:\\\\[\s\S][^\\\\"]*)*"))(?<Numb>(?>[+-]?(?:\d+(?:\.\d*)?|\.\d+)(?:[eE][+-]?\d+)?|(?:[eE][+-]?\d+)))(?<V_KeyVal>(?>\s*(?&Str)\s*:\s*(?&V_Value)\s*))(?<V_Value>(?>(?&Numb)|(?>true|false|null)|(?&Str)|(?&V_Obj)|(?&V_Ary)))(?<V_Ary>\[(?>\s*(?&V_Value)(?&Sep_Ary))*\s*\])(?<V_Obj>{(?>(?&V_KeyVal)(?&Sep_Obj))*\s*}))/m';
$str = '{"device_types":["smartphone"],"isps":["a","B"],"network_types":[],"countries":[],"category":["Jebb","Bush"],"carriers":[],"exclude_carriers":[]}
';
preg_match_all($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