/**
 * $to 宛てにメールを送信する
 *
 * @param string $from 送信元メールアドレス
 * @param string $to 宛先
 * @param string $subject 件名
 * @param string $message 本文
 * @return bool 1;成功 0:失敗
 */
function MailFunction($from, $to, $subject, $message)
{
    // Subject部の文字コードを変換
    $x_subject = mb_convert_encoding($subject, "JIS", "auto");
    $x_subject = base64_enbox3($x_subject);
    $x_subject = "=?iso-2022-jp?B?".$x_subject."?=";

    // Message部の文字コードを変換
    $x_message = htmlspecialchars($message);
    $x_message = str_replace("&", "&", $x_message); // html escape
    if (get_magic_quotes_gpc()) {
        $x_message = stripslashes($x_message);
    }
    $x_message = str_replace("\r\n", "\r", $x_message);
    $x_message = str_replace("\r", "\n", $x_message);
    $x_message = mb_convert_encoding($x_message, "JIS", "auto");

    // メールヘッダを生成
    $gmt = date("Z");
    $gmt_abs  = abs($gmt);
    $gmt_hour = floor($gmt_abs / 3600);
    $gmt_min = floor(($gmt_abs - $gmt_hour * 3600) / 60);
    if ($gmt >= 0) {
        $gmt_flg = "+";
    } else {
        $gmt_flg = "-";
    }
    $gmt_rfc = date("D, d M Y H:i:s ").sprintf($gmt_flg."%02d%02d", $gmt_hour, $gmt_min);

    $headers = "Date: {$gmt_rfc}\n";
    $headers .= "From: {$from}\n";
    $headers .= "Subject: {$x_subject}\n";
    $headers .= "MIME-Version: 1.0\n";
    $headers .= "X-Mailer: PHP/".phpversion()."\n";
    $headers .= "Content-type: text/plain; charset=ISO-2022-JP\n";
    $headers .= "Content-Transfer-Encoding: 7bit";

    // メール送信実行
    if(mail($to, $x_subject, $x_message, $headers)) {
        return true;
    }
    return false;
}

$from = 'from@hoge.com';
$to = 'to@hoge.com';
$subject = '件名';
$body = '本文1行目\n';
$body .= '本文2行目\n';

MailFunction($from, $to, $subject, $body);