在函数之间传递变量 - php

时间:2013-09-25 23:10:18

标签: php function variables

以下是我实际代码的编辑版本:

<?php

include ('login_info.php');

class modernCMS {

var $host;
var $username;
var $password;
var $db;
var $url;


function connect(){
    $con = mysql_connect($this->host, $this->username, $this->password);
    mysql_select_db($this->db, $con) or die(mysql_error());

mysql_set_charset('utf8');

}


function get_coordinates(){

$sql ="select lat, lng from postcodes LIMIT 1;";
    $res = mysql_query($sql) or die(mysql_error());
    while($row = mysql_fetch_assoc($res)){
        $lat = $row['lat'];
        $lng = $row['lng'];

    }
}


 function get_name(){

 $sql ="select name from places WHERE lat=$lat AND lng=$lng LIMIT 1;";
    $res = mysql_query($sql) or die(mysql_error());
    while($row = mysql_fetch_assoc($res)){
        $name = $row['name'];

echo $name;


     }
}


?>

然后在一个单独的文档中,我有一个包含上面的文件。我使用以下函数调用函数get name:

<?=$obj->get_name()?>

get_name实际上包含用于计算两点之间距离的计算,但是因为它的冗长计算我将其从上面的示例中删除了。

重要的是我可以使用$ obj-&gt; get_name()来获取$ lat和$ lng的输出

6 个答案:

答案 0 :(得分:3)

函数在函数范围内运行,因此您在get_coordinates()中设置的变量是局部变量。要创建全局变量,可以使用global关键字:

<?php

function get_coordinates()
{
global $lat, $lng;
$lat = 25;
$lng = 5;
}

function display_coordinates()
{
global $lat, $lng;
echo $lat;
echo $lng;
}

get_coordinates();
display_coordinates();

$GLOBALS数组:

<?php

function get_coordinates()
{
$GLOBALS['lat'] = 25;
$GLOBALS['lng'] = 5;
}

function display_coordinates()
{
echo $GLOBALS['lat'];
echo $GLOBALS['lng'];
}

get_coordinates();
display_coordinates();

但是,这可能不是设置/访问这些变量的最佳方法,因为任何函数都可以随时更改其状态,并且必须调用一个函数来设置它们,然后再调用另一个函数来显示它们。如果您能描述您的具体目标,您可能会得到更好的建议。

实现这一目标的一种更好方法是使用一个类,并将对象传递给您需要它的对象(这个简单示例没有演示正确的encapsulation,但这是一个很好的起点):

<?php

class Coordinates {
  public $lat;
  public $lng;

  public function __construct($lat, $lng) {
    $this->lat = $lat;
    $this->lng = $lng;
  } 

  public function display_coordinates() {
    echo $this->lat . "\n";
    echo $this->lng . "\n";
  }
}

function get_coordinates() {
  return new Coordinates(25, 5);
}

$coords = get_coordinates();
$coords->display_coordinates();


function output_coordinates($coordinates) {
  $coordinates->display_coordinates();
}
output_coordinates($coords);

PHP中常用的另一种方法是在关联数组中传递内容(带索引字符串的数组)。我通常不喜欢这个,因为数组没有声明它想要保留的内容,但它是一个选项:

<?php

function get_coordinates() {
  return array('lat' => 25, 'lng' => 5);
}

function output_coordinates($coordinates) {
  echo $coordinates['lat'] . '\n';
  echo $coordinates['lng'] . '\n';
}

$coords = get_coordinates();
output_coordinates($coords);

答案 1 :(得分:3)

你正在遇到一个范围问题。变量仅适用于声明它们的函数。要使它们可用,您可以显式地将变量传递给函数(您需要确保始终在get_coordinates()之前调用display_coordinates(),否则您将具有未定义的值)或使用全局变量(坏主意)。

最好的方法可能是为它制作一个类(虽然它取决于你打算如何使用它)。您的变量将始终在范围内,并且在初始化变量之前,您不会冒险尝试运行display_coordinates()函数。

class Coordinate
{
    // These are the variables where the coords will be stored.
    // They are available to everything within the {}'s after 
    // "class Coordinate"  and can be accessed with
    // $this->_<varname>.
    protected $_lat;
    protected $_long;

    // This is a special function automatically called when 
    // you call "new Coordinate"
    public function __construct($lat, $long)
    {
        // Here, whatever was passed into "new Coordinate" is
        // now stored in our variables above.
        $this->_lat  = $lat;
        $this->_long = $long;
    }

    // This takes the values are stored in our variables,
    // and simply displays them.
    public function display()
    {
        echo $this->_lat;
        echo $this->_long;
    }
}

// This creates a new Coordinate "object". 25 and 5 have been stored inside.
$coordinate = new Coordinate(25, 5); // 25 and 5 are now stored in $coordinate.
$coordinate->display(); // Since $coordinate already "knows" about 25 and 5
                        // it can display them.

// It's important to note, that each time you run "new Coordinate",
// you're creating an new "object" that isn't linked to the other objects.
$coord2 = new Coordinate(99, 1);
$coord2->display(); // This will print 99 and 1, not 25 and 5.

// $coordinate is still around though, and still knows about 25 and 5.
$coordinate->display(); // Will still print 25 and 5.

您应该阅读Variable ScopeClasses and Objects以了解更多相关信息。

要将它与原始代码放在一起,你可以这样做,

function get_coordinates()
{
     return new Coordinate(25, 5);
}

function display_coordinates($coord)
{
    $coord->display();
}

$c = get_coordinates();
display_coordinates($c);
// or just "display_coordinates(get_coordinates());"


更新问题后编辑

您的代码中存在一些不良做法,但这里有一些快速的步骤来获得您想要的内容。

// Copy the Coordinate class from my answer above, but add two new
// lines before the final "}"
public function getLatitude()  { return $this->_lat; }
public function getLongitude() { return $this->_long; }

// Put the Coordinate class definition before this line
class modernCMS {

/////

// In your code, after this line near the top
var $url;

// Add this
var $coord;

/////

// In your get_coordinates(), change this...
$lat = $row['lat'];
$lng = $row['lng'];

// To this...
$this->coord = new Coordinate($lat, $lng);

/////

// In your get_name(), add two lines to the start of your function.
function get_name(){
    $lat = $this->coord->getLatitude();
    $lng = $this->coord->getLongitude();

与您的问题无关,但您还应该阅读“SQL注入”,因为get_name()中的查询容易受到攻击。这里没什么大不了的,因为无论如何数据来自你的其他查询,但仍然是不要在查询字符串中直接使用参数的好习惯。

答案 2 :(得分:1)

一种方法:

function get_coordinates(&$lat, &$lng)
{
     $lat = 25;
     $lng = 5;
}

function display_coordinates($lat, $lng)
{
     echo $lat;
     echo $lng;
}

$lat = 0;
$lng = 0;

// assign values to variables
get_coordinates( $lat, $lng );

// use function to display them...
display_coordinates ($lat, $lng);

答案 3 :(得分:1)

会话如何? https://www.php.net/manual/en/reserved.variables.session.php

创建新会话

session_start();
/*session is started if you don't write this line can't use $_Session  global variable*/
$_SESSION["newsession"]=$value;

参加会议

session_start();
/*session is started if you don't write this line can't use $_Session  global variable*/

$_SESSION["newsession"]=$value;
/*session created*/

echo $_SESSION["newsession"];
/*session was getting*/

更新会话

session_start();
/*session is started if you don't write this line can't use $_Session  global variable*/

$_SESSION["newsession"]=$value;
/*it is my new session*/

$_SESSION["newsession"]=$updatedvalue;
/*session updated*/

删除会话

session_start();
/*session is started if you don't write this line can't use $_Session  global variable*/

$_SESSION["newsession"]=$value;

unset($_SESSION["newsession"]);
/*session deleted. if you try using this you've got an error*/

答案 4 :(得分:0)

创建Coordinate.class.php文件:

<?php
class Coordinate {
  var $latitude;
  var $longitude;

  public function getLatitude() {
    return $this->latitude;
  }

  protected function setLatitude($latitude) {
    $this->latitude = floatval($latitude);
  }

  public function getLongitude() {
    return $this->longitude;
  }

  protected function setLongitude($longitude) {
    $this->longitude = floatval($longitude);
  }

  public function __construct() {
    // Overload
    if (func_num_args() == 2) {
      $this->setLatitude(func_get_arg(0));
      $this->setLongitude(func_get_arg(1));
    }
    // Default
    else {
      $this->setLatitude(0);
      $this->setLongitude(0);
    }
  }

  public function displayCoordinate() {
    printf("Latitude: %.2f, Longitude: %.2f\n",
      $this->getLatitude(),
      $this->getLongitude());
  }
}

function main() {
  $c = new Coordinate (25, 5);
  $c->displayCoordinate();
}

main();
?>

答案 5 :(得分:0)

更改另一篇文章..我认为更好的方法:

function get_coordinates()
{
    return array(
        "lat" => 25,
        "lng" => 5
    );

}

function display_coordinates($latLongArray)
{
     echo $latLongArray['lat'];
     echo $latLongArray['lng'];
}


// assign values to variables
$latLongArray = get_coordinates();

// use function to display them...
display_coordinates ($latLongArray);