Convert MySQL group concat string to json object structure via PHP - php

Question

I have 2 MySQL tables, the first one is the parent table and second one the child table. These two table share a 1:M relationship. The T_1 contains the list of unique users with some informations. And the T_2 contains all the line data list with coordinates at a specific timestamp for each user. The child table T_2 has a FK that references the PK in the T_1 parent table. I share below the CREATE STATEMENT:
CREATE TABLE `T_1` (
`id` varchar(45) DEFAULT NULL,
`value_1` tinyint(4) NOT NULL,
`personId` varchar(45) NOT NULL,
`value_2` varchar(45) NOT NULL,
`value_3` varchar(45) NOT NULL,
`Value_4` int(11) NOT NULL,
PRIMARY KEY (`personId`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
CREATE TABLE `T_2` (
`personId` varchar(45) NOT NULL,
`timestamp` varchar(45) NOT NULL,
`x` int(11) NOT NULL,
`y` int(11) NOT NULL,
KEY `user_fk_idx` (`personId`),
CONSTRAINT `user_fk` FOREIGN KEY (`personId`) REFERENCES `T_1` (`personId`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
I would like to get as final json result something like that:
[
{
"id": "",
"value_1": true,
"personId": "1",
"value_2": "test",
"value_3": "test",
"value_4": 10,
"lineData": [
{
"timestamp": "some_date",
"x": 100,
"y": 250
},
{
"timestamp": "some_date",
"x": 100,
"y": 350
}
]
},
{
"id": "",
"value_1": true,
"personId": "2",
"value_2": "test",
"value_3": "test",
"value_4": 10,
"lineData": [
{
"timestamp": "some_date",
"x": 50,
"y": 450
},
{
"timestamp": "some_date",
"x": 80,
"y": 550
}
]
}
]
This is the first query selection that I have made in order to get the aggregation of all the T_2 records for each T_1.personId:
SELECT T_1.personId,GROUP_CONCAT(CONCAT(T_2.timestamp, T_2.x, T_2.y) SEPARATOR ' ')
FROM T_1
JOIN T_2
ON T_1.personId=T_2.personId
GROUP BY personId;
Except that I need to add also id, value_1, value_2, value_3, value_4, the query aggregation seems correct by I'm still far away from the expected result:
By using the PDO::FETCH_ASSOCquery fetch within PHP I get actually the similar expected array result.
But the main problem is that the linedata aggregation is just in a single string format grouped and concatenated all together, not in an object structure form. (screen below)
I attach the example data below from the query selection:
array(7) {
["id"]=>
NULL
["value_1"]=>
string(1) "0"
["personId"]=>
string(2) "1"
["value_2"]=>
string(9) "test"
["value_3"]=>
string(4) "test"
["value_4"]=>
string(2) "10"
["linedata"]=>
string(359) "2018/09/15 10:00:05 AM1100950 2018/09/15 10:00:07 AM1100850 2018/09/15 10:00:09 AM1180800 2018/09/15 10:00:10 AM1280800 2018/09/15 10:00:15 AM1380800 2018/09/15 10:00:17 AM1480800 2018/09/15 10:00:20 AM1900800 2018/09/15 10:00:25 AM1930750 2018/09/15 10:00:40 AM1910440 2018/09/15 10:00:45 AM1250460 2018/09/15 10:01:25 AM1100455 2018/09/15 10:01:29 AM1100655"
}
}
Maybe is it needed to concatenate the square and curly brackets within the selection query?
Can someone suggest me how to get the correct separated structure for linea data? I supposed that we need to use also some post-process PHP stuff in order to get the exact desired output structure.
Update
Following the #Salman A's suggestion, I have tweak the query as below:
GROUP_CONCAT(CONCAT_WS(', ',timestamp,x, y) SEPARATOR '; ') as linedata_0
And I have stored the result of the query within $query_result.
Then I have made a nested foreach in order to explode each row with ; and each value of each row with , in $query_result['linedata_0']. And I have put the exploded result in a new key called linedata_1. As showed below:
foreach ($query_result as $q_r){
$first_split = explode(";", $q_r["linedata_0"]);
foreach ($first_split as $f_s){
$second_split = explode(",", $f_s);
$query_result["linedata_1"][]= $second_split;
}
}
I have removed the $query_result[0]["linedata_0"] element. And after that I have assigned the key values to each $query_result['linedata_1'] sub-arrays and store in a new element called $query_result['linedata']. After that I have remove the old $query_result['linedata_1'] element with unset command and in the last foreach I have cast the x and y values from string to integer:
unset($query_result[0]["linedata_0"]);
foreach(($query_result["linedata_1"]) as $q_r) {
$keys = array('timestamp', 'x', 'y');
$query_result["linedata"][] = array_combine($keys, $q_r);
}
unset($query_result["linedata_1"]);
$index = 0;
foreach($query_result["linedata"] as $index=>$val) {
$query_result["linedata"][$index]["x"] = (int) $val["x"];
$query_result["linedata"][$index]["y"] = (int) $val["y"];
$index++;
}
With these PHP post-process operations I got exactly the expected result.Probably this post-process steps within php are not well optimized, but they do the trick for me. If someone of us has a more optimized workaround solution please share it. Thanks.