Column Extract

array_column extracts one named field from each row.

column_extract.php

<?php
$field = ;
$rows = [
    ["name" => "Ada", "city" => "London", "role" => "admin"],
    ["name" => "Rasmus", "city" => "Copenhagen", "role" => "author"]
];
$values = array_column($rows, $field);
$summary = implode(",", $values);

echo "field=" . $field . "\n";
echo "values=" . $summary . "\n";

<?php
$field = ;
$rows = [
    ["name" => "Ada", "city" => "London", "role" => "admin"],
    ["name" => "Rasmus", "city" => "Copenhagen", "role" => "author"]
];
$values = array_column($rows, $field);
$summary = implode(",", $values);

echo "field=" . $field . "\n";
echo "values=" . $summary . "\n";

<?php
$field = ;
$rows = [
    ["name" => "Ada", "city" => "London", "role" => "admin"],
    ["name" => "Rasmus", "city" => "Copenhagen", "role" => "author"]
];
$values = array_column($rows, $field);
$summary = implode(",", $values);

echo "field=" . $field . "\n";
echo "values=" . $summary . "\n";

one field from many rows Column extraction turns a list of records into a list of selected values.