如何在php foreach循环中使用函数？ [重复]

I want to use a function inside my loop, in order to print my data in a nice format into my table.

$pdo = Database::connect();
$sql = 'SELECT * FROM data ORDER BY id ASC';
foreach ($pdo->query($sql) as $row) {

    function formatSizeUnits($bytes)
    {
        if ($bytes >= 1073741824) {
            $bytes = number_format($bytes / 1073741824, 2).' GB';
        } elseif ($bytes >= 1048576) {
            $bytes = number_format($bytes / 1048576, 2).' MB';
        } else {
            $bytes = '0 bytes';
        }

        return $bytes;
    }


    $bytes = $row['fileSize'];
    formatSizeUnits($bytes);

    echo('<td>'.$bytes.'</td>');
}

But now I get only the first entry of the database table. How can I get this work?

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Using and declaring your function are two different things. You only need to declare your function once. It throws an error because it is trying to re-declare it in the next loop.

Like this:

$pdo = Database::connect();
$sql = 'SELECT * FROM data ORDER BY id ASC';
foreach ($pdo->query($sql) as $row) {

    $bytes = $row['fileSize'];
    formatSizeUnits($bytes);

    echo('<td>'.$bytes.'</td>');
}

function formatSizeUnits($bytes)
{
    if ($bytes >= 1073741824) {
        $bytes = number_format($bytes / 1073741824, 2).' GB';
    } elseif ($bytes >= 1048576) {
        $bytes = number_format($bytes / 1048576, 2).' MB';
    } else {
        $bytes = '0 bytes';
    }

    return $bytes;
}

Also regarding your question:

You are not passing the $bytes to formatSizeUnits() by reference, but it is returning the value, you need to overwrite it.

$bytes = formatSizeUnit($bytes);

You can't declare a function in loop. Instead using it in loop define it outside the loop and call in loop once only