如何返回全局变量的分支条件在php - how to return global variable by the branch condition in php?

我正在编写这个web应用程序来计算两个城市之间的航空旅行距离，如果我填写出发机场和目的地机场，它将直接计算。如果我填写了"via"输入字段，那么我必须把它作为一个中间城市来计算旅行距离。我不知道如何设置条件取决于via是否被填满。我的代码哪里有问题?我有输入字段连接到我的数据库和检索信息。这是我的html部分:

  <div>
        From
        <div class="textinput">
            <input type="text" id="dept" name="departure" placeholder="City name or aiport code" >
        </div>
    </div>
    <div>
        To
        <div>
            <input type="text" id="dest" placeholder="City name or airport code" >
        </div>
    </div>
    <div>
        Via
        <div>
            <input type="text" id="via" placeholder="City name or airport code" >
        </div>
    </div>

下面是php:

       if(isset($_POST['dept'], $_POST['dest'])){
      $dept=$_POST['dept'];
      $dest=$_POST['dest'];
   }
mysql_connect("localhost","ccc","aaa") or die (mysql_error());
    mysql_select_db("ccc") or die(mysql_error());
    $miles = 0;
    $co2 = 0;
    if(isset($_POST['via'])){
        indirect();
    }
    else{
        direct();
    }

    function direct(){
    $strSQL1 = "SELECT display, lat, longi FROM airport WHERE display = '$dept'";
    $rs1 = mysql_query($strSQL1);
    $row1 = mysql_fetch_array($rs1);
    $lat1= $row1['lat'];
    $long1= $row1['longi'];
    $strSQL2 = "SELECT display, lat, longi FROM airport WHERE display = '$dest'";
    $rs2 = mysql_query($strSQL2);
    $row2 = mysql_fetch_array($rs2);
    $lat2= $row2['lat'];
    $long2= $row2['longi'];
    $earthradius = 6366.707;    
    $km_to_miles = 1/1.609344;
    $dlat = ($lat2-$lat1) * (M_PI / 180);
    $dlon = ($long2-$long1) * (M_PI / 180);
    $a = sin($dlat / 2) * sin($dlat / 2) + sin($dlon / 2) * sin($dlon / 2) * cos($lat1 * (M_PI / 180)) * cos($lat2 * (M_PI / 180));
    $c = 2 * atan2(sqrt($a), sqrt(1-$a));
    $d = $c * $earthradius;
    $miles = $d * $km_to_miles;
    $co2 = (($miles / 41.986) * 20.88 * 1.9) / 2204.6; 
    }
    function indirect(){
    $strSQL1 = "SELECT display, lat, longi FROM airport WHERE display = '$dept'";
    $rs1 = mysql_query($strSQL1);
    $row1 = mysql_fetch_array($rs1);
    $lat1= $row1['lat'];
    $long1= $row1['longi'];
    $strSQL2 = "SELECT display, lat, longi FROM airport WHERE display = '$dest'";
    $rs2 = mysql_query($strSQL2);
    $row2 = mysql_fetch_array($rs2);
    $lat2= $row2['lat'];
    $long2= $row2['longi'];
    $strSQL3 = "SELECT display, lat, longi FROM airport WHERE display = '$via'";
    $rs3 = mysql_query($strSQL3);
    $row3 = mysql_fetch_array($rs3);
    $lat3= $row3['lat'];
    $long3= $row3['longi'];
    $earthradius = 6366.707;    
    $km_to_miles = 1/1.609344;
    $dlat1 = ($lat3-$lat1) * (M_PI / 180);
    $dlon1 = ($long3-$long1) * (M_PI / 180);
    $a1 = sin($dlat1 / 2) * sin($dlat1 / 2) + sin($dlon1 / 2) * sin($dlon1 / 2) * cos($lat1 * (M_PI / 180)) * cos($lat3 * (M_PI / 180));
    $c1 = 2 * atan2(sqrt($a1), sqrt(1-$a1));
    $d1 = $c1 * $earthradius;
    $miles1 = $d1 * $km_to_miles;
    $dlat2 = ($lat3-$lat2) * (M_PI / 180);
    $dlon2 = ($long3-$long2) * (M_PI / 180);
    $a2 = sin($dlat2 / 2) * sin($dlat2 / 2) + sin($dlon2 / 2) * sin($dlon2 / 2) * cos($lat2 * (M_PI / 180)) * cos($lat3 * (M_PI / 180));
    $c2 = 2 * atan2(sqrt($a2), sqrt(1-$a2));
    $d2 = $c2 * $earthradius;
    $miles2 = $d2 * $km_to_miles;
    $miles = $miles1 + $miles2;
    $co2 = (($miles / 41.986) * 20.88 * 1.9) / 2204.6; 
    }

    echo json_encode(array('co2' => $co2,'miles'=>$miles));

  ?>

我想你对变量$co2和$miles的范围有问题。

把你的echo json_encode(array('co2' => $co2,'miles'=>$miles));放在direct()和indirect()里面

if(isset($_POST['via'])){
        indirect($dept, $dest);
    }
    else{
        direct($dept, $dest);
    }

    function direct($dept, $dest){

//do some stuff here
}
    function indirect($dept, $dest){
//do some stuff here
}

你必须从你的函数中返回一些东西，像这样:

function direct($dept, $dest)
{
    // ...
    return [$co2, $miles];
}
function indirect($dept, $dest, $via)
{
    // ...
    return [$co2, $miles];
}

返回一个数组，$co2和$miles分别是第一个和第二个元素。然后，在代码中:

if (isset($_POST['via'])) {
    list($co2, $miles) = indirect($dept, $dest, $_POST['via']);
} else {
    list($co2, $miles) = direct($dept, $dest);
}

也就是说，你真的应该考虑使用PDO/mysql，并学习准备语句;或者，至少应该使用mysql_real_escape_string()转义SQL语句中的变量，例如:

$strSQL1 = sprintf("SELECT display,lat,longi FROM airport WHERE display='%s'", 
    mysql_real_escape_string($dept)
);