Ubuntu 16.04 安装 php7 时 SQLSRV 驱动安装问题

Question

使用以下步骤安装了 sqlsrv，但无法连接 sql server express 2017

步骤 1. 安装 PHP

apt-get update
apt-get -y install php7.0 mcrypt php7.0-mcrypt php-mbstring php-pear php7.0-dev php7.0-xml

步骤 2. 安装先决条件

curl https://packages.microsoft.com/keys/microsoft.asc | sudo apt-key add -
curl https://packages.microsoft.com/config/ubuntu/16.04/prod.list | sudo tee /etc/apt/sources.list.d/mssql-release.list

sudo apt-get update
sudo ACCEPT_EULA=Y apt-get install msodbcsql mssql-tools
sudo apt-get install unixodbc-dev
echo 'export PATH="$PATH:/opt/mssql-tools/bin"' >> ~/.bash_profile
echo 'export PATH="$PATH:/opt/mssql-tools/bin"' >> ~/.bashrc
source ~/.bashrc

步骤 3. 安装适用于 Microsoft SQL Server 的 PHP 驱动程序

sudo pear config-set php_ini `php --ini | grep "Loaded Configuration" | sed -e "s|.*:\s*||"` system
sudo pecl install sqlsrv
sudo pecl install pdo_sqlsrv

db.php（运行此脚本后无消息显示）

<?php
$serverName = "servername"; //serverName\instanceName

// Since UID and PWD are not specified in the $connectionInfo array,
// The connection will be attempted using Windows Authentication.
$connectionInfo = array( "Database"=>"database", "UID"=>"user", "PWD"=>"password");
$conn = sqlsrv_connect( $serverName, $connectionInfo);

if( $conn ) {
     echo "Connection established.<br />";
}else{
     echo "Connection could not be established.<br />";
     die( print_r( sqlsrv_errors(), true));
}
?>

你能帮忙吗？ubuntu 16.04.1 运行上述脚本 db.php 后显示空白页。