如何检查我的服务器上是否安装了 PEAR？

我收到如下错误：

警告：include_once(Net/SMTP.php) [function.include-once]: 无法打开流：第 348 行 /usr/local/lib/php/Mail/smtp.php 中没有此类文件或目录

警告：include_once() [function.include]：无法在 /usr/local 中打开 'Net/SMTP.php' 进行包含 (include_path='.:/usr/lib/php:/usr/local/lib/php') /lib/php/Mail/smtp.php 第 348 行

致命错误：在第 349 行的 /usr/local/lib/php/Mail/smtp.php 中找不到类“Net_SMTP”

My code:

require_once 'Mail.php';

$from = "[email protected] /cdn-cgi/l/email-protection>";

$to = "[email protected] /cdn-cgi/l/email-protection>";
$subject = "Hi!";
$body = "Hi,\n\nHow are you?";

$host = "mail.example.com";

$username = "me";
$password = "test";

$headers = array ('From' => $from,
  'To' => $to,
  'Subject' => $subject);

$smtp = Mail::factory('smtp',
  array ('host' => $host,
    'auth' => true,
    'username' => $username,
    'password' => $password));
$mail = $smtp->send($to, $headers, $body);

if (PEAR::isError($mail)) {
  echo("<p>" . $mail->getMessage() . "</p>");
 } else {
  echo("<p>Message successfully sent!</p>");
 }

如果您有 ssh 访问权限，则可以登录并运行

which pear

如果安装了它会打印类似这样的内容

/usr/bin/pear