add values into multidimensional array - php

Question

I have a foreach loop that goes through a list of items. For each of these items, I have a while loop that grabs data out of a database.
$output = array();
//$reference is a multidimensional array has been passed to this page
where the element `color` contains the color I want.
foreach ($reference as $c) {
$color = $c['color'];
$query = "SELECT DISTINCT name FROM $table where colorPreference = $color";
$exquery = mysqli_query($con, $customerQuery);
while ($row = mysqli_fetch_array($exquery)) {
$person = $row['person'];
array_push($output[$color], $person);
}
}
So this loops through, the first time searching 'red', and finding 5 people in the fake table who like red. Next, 'blue', where it finds 1 person, and then 'green' where it finds 3.
If I look at the individual results, my first array has "red, blue, green" and my second array has these lists of names.... I just don't know how to add them into an array together.
I'm trying to build an array like this:
Array
(
[Red] => Array
(
[0] => John
[1] => Sally
[2] => Bob
...
)
[Blue] => Array
(
[0] => Luke
)
[Green] => Array
(
..etc...
)
I'm not using array_push correctly though - I'm getting an Warning: Illegal offset type error. What am I doing wrong?

Answer 1

It's been a while since I've worked with PHP, but I think you need to initialize each "color" array that you're going to push into. So...
$output = array();
//$reference is a multidimentional array has been passed to this page
where the element `color` contains the color I want.
foreach ($reference as $c) {
$color = $c['color'];
$query = "SELECT DISTINCT name FROM $table where colorPreference = $color";
$exquery = mysqli_query($con, $customerQuery);
while ($row = mysqli_fetch_array($exquery)) {
$person = $row['person'];
if (!array_key_exists($color, $output)) {
$output[$color] = array();
}
array_push($output[$color], $person);
}
}

Answer 2

Try changing:
array_push($output[$color], $person);
Into:
$output[$color][] = $person;
From the manual on array_push:
Note: If you use array_push() to add one element to the array it's better to use $array[] = because in that way there is no overhead of calling a function.
Note: array_push() will raise a warning if the first argument is not an array. This differs from the $var[] behaviour where a new array is created.