$re = '/,"sql_queries":".*?,"/m';
$str = '{"method":"GET","path":"/REDACTED","format":"json","controller":"REDACTED","action":"validate_token","status":200,"duration":30.26,"view":2.67,"db":5.88,"pid":10109,"sql_queries":"\' = 65593\\nUser Load (0.86) SELECT `users`.* FROM `users` WHERE `users`.`id` 3:59:58\', `tokens` = \'{\\\\\\"REDACTED\\\\\\":{\\\\\\"token\\\\\\":\\\\\\"REDACTED/W\\\\\\",\\\\\\"expiry\\\\\\":1550795150},\\\\\\"REDACTED\\\\\\":{\\\\\\"token\\\\\\":\\\\\\"REDACTED/\\\\\\",\\\\\\"expiry\\\\\\":1550795151},\\\\\\"REDACTED\\\\\\":{\\\\\\"token\\\\\\":\\\\\\REDACTED\\\\",\\\\\\"expiry\\\\\\":1550795151},\\\\\\"REDACTED\\\\\\":{\\\\\\"token\\\\\\":\\\\\\"REDACTED\\\\\\",\\\\\\"expiry\\\\\\":1550795152},\\\\\\"REDACTED\\\\\\":{\\\\\\"token\\\\\\":\\\\\\"$REDACTED\\\\\\",\\\\\\"expiry\\\\\\":1550795152},\\\\\\"REDACTED-g\\\\\\":{\\\\\\"token\\\\\\":\\\\\\"$REDACTED\\\\\\",\\\\\\"expiry\\\\\\":1550795153},\\\\\\"REDACTED\\\\\\":{\\\\\\"token\\\\\\":\\\\\\"REDACTED\\\\\\",\\\\\\"expiry\\\\\\":1550795154},\\\\\\"REDACTED\\\\\\":{\\\\\\"token\\\\\\":\\\\\\"REDACTED\\\\\\",\\\\\\"expiry\\\\\\":1550800798}}\' WHERE `users`.`id` = 65593\\n (0.98) COMMIT\'","@timestamp":"2019-02-21T23:59:58.015Z","@version":"1","message":"[200] GET / "}';
$subst = " ";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
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