check-utf8-db.php

<?php

// $pdo = new PDO(...)

$charsets = array('UTF-8', 'ISO-8859-1');

$tables = array(
    'events' => array(
        'title',
        'description',
    ),
    'locations' => array(
        'title',
        'description',
    ),
);

foreach ($tables as $table => $fields) {
    $result = $pdo->query('SELECT id, ' . implode(', ', $fields) . ' FROM ' . $table);
    
    while ($row = $result->fetch()) {
        foreach ($fields as $field) {
            if (($encoding = mb_detect_encoding($row[$field], $charsets, true)) != 'UTF-8') {
                echo $table . '[' . $row['id'] . ']' . '.' . $field . ': ' . $encoding . "\n";

                $converted = iconv($encoding, 'UTF-8', $row[$field]);
                $stmt = $pdo->prepare('UPDATE ' . $table . ' SET ' . $field . ' = ? WHERE id = ?');
                $stmt->execute(array($converted, $row['id']));
            }
        }
    }
}