mysql get records with relation in usable structure - php

Question

Say I have 2 tables. parent & child where a parent can have many children.
I want to get the data in the following structure so:
[
{ parent_id:1, children: [{child_id: 1, parent_id:1},{ child_id:2, parent_id:1}],
{ parent_id:2, children: [{child_id: 3, parent_id:2},{ child_id:4, parent_id:2}],
{ parent_id:3, children: [{child_id: 5, parent_id:3},{ child_id:6, parent_id:3}]
]
JOIN gives me duplicate parent data for each child, and GROUP BY parent_id only gives me 1 child per parent.
Currently my solution is: SELECT * from parent loop through the results and then SELECT * FROM child WHERE parent_id = :parent_id. I feel there has to be a better way.
Is MySQL capable of performing this in fewer queries, if so how would I go about it?
EDIT: Hacky solution based on using GROUP_CONCAT:
$q = "SELECT p.*, GROUP_CONCAT(c.id,'|#|', c.column_2, '|#|', c.column3, '|#|', c.column4 SEPARATOR '###') AS children
FROM parent p
INNER JOIN child c ON p.id = c.parent_id";
$parents= query($q);
foreach ($parents as &$parent) {
$children = explode('###', $parent->children);
foreach ($children as &$child){
$child = array_combine(['id','col1','col2','col3'], explode('|#|', $child));
}
$parent->children = $children;
}
Essentially get the string with separators, explode into records, then explode into columns and remap the column values with hardcoded column names.
Leaving this open to tidier solutions.
If there are no better solutions, which would be more efficient.
1 query:group_concat where php manipulates the data into the desired structure.
n* queries: get all parents, then loop through them and get each parents children.
2 queries: get all parents, get all children, loop through and map them (currently using this)

Answer 1

I think you can use GROUP_CONCAT:
SELECT p.parent_id, GROUP_CONCAT(c.child_id) AS childs
FROM parent p
JOIN child c
ON p.parent_id = c.parent_id
GROUP BY p.parent_id