<?php
require_once __DIR__ . '/db_conn.php';
$pdo = db_conn();
$cols = $pdo->query("SHOW COLUMNS FROM edu_users")->fetchAll(PDO::FETCH_ASSOC);
foreach ($cols as $c) {
    echo $c['Field'] . '|' . $c['Type'] . '|' . $c['Null'] . '|' . $c['Key'] . '|' . ($c['Default'] ?? 'NULL') . PHP_EOL;
}
echo "---sample---" . PHP_EOL;
$rows = $pdo->query("SELECT member_id, intra_pw FROM edu_users ORDER BY member_id LIMIT 5")->fetchAll(PDO::FETCH_ASSOC);
foreach ($rows as $r) {
    $pw = (string)($r['intra_pw'] ?? '');
    $prefix = substr($pw, 0, 4);
    echo $r['member_id'] . '|len=' . strlen($pw) . '|prefix=' . $prefix . PHP_EOL;
}