Create multidimensional array from rows of data - php

Question

I have a database with project entries. Each entry has a project title, datestamp, the user who entered it, and a comment. I am trying to format this data as JSON for reporting and charts.
I want an array for each project name, and inside that array an array for each entry.
I've tried several approaches but I haven't had much luck yet.
if ($result = $mysqli->query("SELECT * FROM project_entries"))
// WHERE WEEK(date) = WEEK(current_date) ORDER BY project_name
{
while ($row = mysqli_fetch_array($result)) {
$entry_array = array();
$row_array['project_name'] = $row['project_name'];
$comment = $row['comment'];
$entry = array (
'comment' => $comment,
);
$row_array['entries'] = $entry;
if ( !in_array($row['project_name'], $projects, false ))
{
array_push($projects, $row_array);
}
}
}
Outputs:
[
{
"project_name": "Logo Design",
"entries": {
"comment": "Worked on a thing"
}
},
{
"project_name": "Logo Design",
"entries": {
"comment": "Created some stuff"
}
},
While I want:
{
"project_name": "Logo Design",
"entries": {
"comment": "Worked on a thing",
"comment": "Created some stuff"
}
}

Answer 1

This should do the trick. You can use the project name as an array key. In order to prevent the string keys from showing up in your output array, you can use array_values to convert them to numeric keys.
$projects = array();
while ($row = mysqli_fetch_array($result)) {
$projects[$row['project_name']]['project_name'] = $row['project_name'];
$projects[$row['project_name']]['entries'][] = array('comment' => $row['comment']);
}
echo json_encode(array_values($projects));
What was going wrong with your previous code:
if ($result = $mysqli->query("SELECT * FROM project_entries")) {
while ($row = mysqli_fetch_array($result)) {
$entry_array = array(); // This does not appear to be used
// With each iteration of the while loop, you create a new array of
// project information (project name and entries array with one comment)
$row_array['project_name'] = $row['project_name'];
$comment = $row['comment'];
$entry = array ('comment' => $comment);
$row_array['entries'] = $entry;
// The $projects array is an array of arrays, but $row['project_name'] is
// a string. Checking if this string is in an array of arrays will always
// be false, so the array_push should always execute.
if (!in_array($row['project_name'], $projects, false )) {
// Adds the new project array to the projects array
array_push($projects, $row_array);
}
// This is not producing what you want because you are adding a new
// array to $row_array each time the loop runs
}
}
Why the code I suggested works:
$projects = array(); // Empty array to hold all the projects
while ($row = mysqli_fetch_array($result)) {
// Using the project name from the database as an array key in the array we are
// constructing keeps the projects unique in that array.
// The first time a new project name occurs, this will create a new sub-array
// within $projects with project_name => the new project name. This value will
// be overwritten on subsequent occurrences of the same project name.
$projects[$row['project_name']]['project_name'] = $row['project_name'];
// For each iteration, this will add a comment to the 'entries' array in the
// project array with the key $row['project_name'].
$projects[$row['project_name']]['entries'][] = array('comment' => $row['comment']);
// For example, with the first iteration of the array we create the following:
//
// $projects['Logo Design'][
// 'project_name' =>'Logo Design',
// 'entries' => [0 => ['comment' => 'Worked on a thing'] ] ]
//
// with the second iteration, the project name is overwritten (with same project name)
// and another comment array is added to the entries array
//
// $projects['Logo Design'][
// 'project_name' =>'Logo Design',
// 'entries' => [0 => ['comment' => 'Worked on a thing'],
// 1 => ['comment' => 'Created some stuff'] ] ]
}
// If you just did echo json_encode($projects), you would not get the format you want,
// because of the string keys. Try it without the array_values() to see what I mean.
echo json_encode(array_values($projects));

Answer 2

Maybe something like that?
Use project id to build target array.
while ($row = mysqli_fetch_array($result) {
if (!isset($projects[$row['id']]))
{
$projects[$row['id']] = [
'project_name' => $row['project_name'],
'entries' => [],
];
}
$projects[$row['id']]['entries'][] = [
'comment' => $row['comment'],
];
}