$re = '/loc=((?:(?!\s,).)*)/m';
$str = 'loc=/abc/flows/timespan/2021-08-10T11:35:00+00:00_2021-08-10T12:35:00+00:00/ip_initiate/10.101.10.20/data.ext
loc=\\"{\\"type\\":1,\\"namespace\\":\\"flows\\",\\"appIds\\":\\"10,11,12\\",\\"path_bar\\":\\"[\\\\\\"ip_initiate=10.1.120.11\\\\\\"]\\",\\"2021-08-10T11:35:00+00:00_2021-08-10T12:35:00+00:00\\\\/ip_initiate\\\\/10.1.120.11\\\\/http_code\\\\/200\\",\\"restrict\\":null}\\"", day=xyz
loc=\\"{\\"type\\":1,\\"namespace\\":\\"flows\\",\\"appIds\\":\\"10,11,12\\",\\"path_bar\\":\\"[\\\\\\"ip_initiate=10.1.120.11\\\\\\"]\\",\\"2021-08-10T11:35:00+00:00_2021-08-10T12:35:00+00:00\\\\/ip_initiate\\\\/10.1.120.11\\\\/http_code\\\\/200\\",\\"restrict\\":null}\\"", ip=10.10.10.10
loc=\\"/timespan/2021-09-12T14:21:00/ip_responder/10.10.10.10/,country=xyz,dns=example.com,http:code=2548:111:0:0:0:0:182.25.236.2:10\\"';
preg_match_all($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