Bulk INSERT in a Single Statement

<?php
function bulkInsert(PDO $db, string $table, array $rows): int {
    if (!$rows) return 0;
    $cols    = array_keys($rows[0]);
    $colList = '`' . implode('`,`', $cols) . '`';
    $rowPh   = '(' . implode(',', array_fill(0, count($cols), '?')) . ')';
    $allPh   = implode(',', array_fill(0, count($rows), $rowPh));

    $sql = "INSERT INTO `$table` ($colList) VALUES $allPh";
    $params = [];
    foreach ($rows as $r) foreach ($cols as $c) $params[] = $r[$c] ?? null;
    $stmt = $db->prepare($sql);
    $stmt->execute($params);
    return $stmt->rowCount();
}

bulkInsert($db, 'events', [
    ['user_id'=>1,'event'=>'login'],
    ['user_id'=>2,'event'=>'signup'],
    ['user_id'=>1,'event'=>'view_page'],
]);