"what is the best way to insert multiple rows in php pdo mysql?" Code Answer

You have at least these two options:

$rows = [(1,2,3), (4,5,6), (7,8,9) ... ];

$sql = "insert into `table_name` (col1, col2, col3) values (?,?,?)";

$stmt = $db->prepare($sql);

foreach($rows as $row)
{
    $stmt->execute($row);
}

OR:

$rows = [(1,2,3), (4,5,6), (7,8,9) ... ];

$sql = "insert into `table_name` (col1, col2, col3) values ";

$paramArray = array();

$sqlArray = array();

foreach($rows as $row)
{
    $sqlArray[] = '(' . implode(',', array_fill(0, count($row), '?')) . ')';

    foreach($row as $element)
    {
        $paramArray[] = $element;
    }
}

// $sqlArray will look like: ["(?,?,?)", "(?,?,?)", ... ]

// Your $paramArray will basically be a flattened version of $rows.

$sql .= implode(',', $sqlArray);

$stmt = $db->prepare($sql);

$stmt->execute($paramArray);

As you can see the first version features a lot simpler code; however the second version does execute a batch insert. The batch insert should be faster, but I agree with @BillKarwin that the performance difference will not be noticed in the vast majority of implementations.