如何在PHP中添加数字“1”作为电话号码的前缀?

我想在电话号码变量$toNumbers前面添加数字1“1”。我已经尝试了PHP字符串

$toNumbers = '1'.$toNumbers;

在电话号码前附加1,但无法使其生效。我在这里做错了什么?

下面是来自vTiger SMS模块的,我需要在数字格式前面加一个1,以便发送。我想在每个数字前面加上1,以便短信模块正确发送。问题是,我的所有电话号码都存储为(xxx)xxx-xxxx,而不是1(xxx)xxx-xxx。

public function send($message, $toNumbers) {

    if(!is_array($toNumbers)) {
        $toNumbers = '1'.$toNumbers;
        $toNumbers = array($toNumbers);
    }


    $params = $this->prepareParameters();

    $params['text'] = $message;
    $params['to'] = implode(',', $toNumbers);


    $serviceURL = $this->getServiceURL(self::SERVICE_SEND);
    $httpClient = new Vtiger_Net_Client($serviceURL);
    $response = $httpClient->doPost($params);
    $responseLines = split("\n", $response);

    $results = array();
    $i=0;
    foreach($responseLines as $responseLine) {
        $responseLine = trim($responseLine);
        if(empty($responseLine)) continue;

        $result = array( 'error' => false, 'statusmessage' => '' );
        if(preg_match("/ERR:(.*)/", trim($responseLine), $matches)) {
            $result['error'] = true;
            $result['to'] = $toNumbers[$i++];
            $result['statusmessage'] = $matches[0]; // Complete error message
        } else if(preg_match("/ID: ([^ ]+)TO:(.*)/", $responseLine, $matches)) {
            $result['id'] = trim($matches[1]);
            $result['to'] = trim($matches[2]);
            $result['status'] = self::MSG_STATUS_PROCESSING;
        } else if(preg_match("/ID: (.*)/", $responseLine, $matches)) {
            $result['id'] = trim($matches[1]);
            $result['to'] = $toNumbers[0];
            $result['status'] = self::MSG_STATUS_PROCESSING;
        } 
        $results[] = $result;
    } 
    return $results;
}