Php HTTP错误:HTTP头后不存在数据

Php HTTP错误:HTTP头后不存在数据,php,mysql,soap,Php,Mysql,Soap,我正在尝试查询数据库并将值返回给客户端。这是我的代码,有两个函数。速率应该以db为单位 public function connect($description){ //creating connection $con = new mysqli('localhost','root','','ci_vetro'); //mysql_connect('localhost','root','') or die("Connection Error: ".mysql_er

我正在尝试查询数据库并将值返回给客户端。这是我的代码,有两个函数。速率应该以db为单位

    public function connect($description){

    //creating connection
    $con = new mysqli('localhost','root','','ci_vetro');
    //mysql_connect('localhost','root','') or die("Connection Error: ".mysql_error());
    //mysql_select_db('ci_vetro');

    //check connection
    if($con->connect_error):
        die('Connection Error: '. $con->connect_error);
    endif;

    $sql= "SELECT * from. exchange_rates where description=.'$description'.";
    $result= $con->query($sql);

    if($result->num_rows > 0):
        while($row = $result->fetch_assoc()) :
           $rate=$row["rate"]. "<br>";
        endwhile;
    else:
        echo "0";
    endif;

    $con->close();
    return $rate;

}
    public function getCurrency($currency) {

        $rate=connect($currency);

    switch ($currency){
        case 'USD':
            return int($rate);
        break;
        default:
          return 0;
        break;
    }
}
公共功能连接($description){
//创建连接
$con=newmysqli('localhost','root','','ci_vetro');
//mysql_connect('localhost','root','')或die(“连接错误:”.mysql_Error());
//mysql_select_db('civetro');
//检查连接
如果($con->connect\u错误):
die('Connection Error:'。$con->connect_Error);
endif;
$sql=“SELECT*from.exchange\u rates,其中description=.$description.”;
$result=$con->query($sql);
如果($result->num_rows>0):
而($row=$result->fetch_assoc()):
$rate=$row[“rate”]。“
”; 结束时; 其他: 回声“0”; endif; $con->close(); 回报率:$; } 公共函数getCurrency($currency){ $rate=connect($currency); 交换机(货币){ “美元”一案: 返回整数(费率); 打破 违约: 返回0; 打破 } }
mysql->query如果查询有语法错误,则返回false。因此,您尝试获取布尔变量的“num_行”。启用错误以查看发生了什么<代码>$sql=“选择*自.exchange\u汇率,其中description=。$description.”