array_sum 以字符串形式返回值的总和

Question

这看起来应该很简单，但我不断得到意想不到的输出。我正在尝试访问 SQL 数据库中的指定行，每个行都包含一个数值，然后计算这些值的总和。即使在我将值的数据类型设置为浮点数之后，PHP 仍将值连接起来，就好像它们是字符串一样。我的代码：

$query = "SELECT * FROM populations WHERE username ='{$_SESSION[name]}' AND region_name = 'region'"
$query .= "AND city_name = 'city'"; 
$result = mysqli_query($connection, $query);

while($row = mysqli_fetch_assoc($result)) {
$population_value = $row['population_value'];

$population_value = is_array($population_value) ? $population_value : array($population_value);

foreach($population_value as $value){
echo $value;
}       

echo array_sum($population_value);
}

我也试过了：

$total = array("");

foreach($population_value as $value){
floatval($value);
array_push($total, $value);
echo $value;
}

echo array_sum($total);

我的输出总是类似于：100002000030000 10,000 20,000 和 30,000 是每个总体的值。

我已经使用foreach 成功计算了总和，其中的值不是从 MySQL 中检索到的。 这是怎么回事？

Answer 1

$query = "SELECT * FROM populations WHERE username ='{$_SESSION[name]}' AND region_name = 'region'"
$query .= "AND city_name = 'city'"; 
$result = mysqli_query($connection, $query);

while($row = mysqli_fetch_assoc($result)) {
$population_value = $row['population_value']; 

//This is actually rewriting the array or NOT adding the value to it.
$population_value = is_array($population_value) ? $population_value : array($population_value);

//ok, so you're going to repeatedly output this?
foreach($population_value as $value){
echo $value; 
}       

echo array_sum($population_value);
}

我想你想要的是这样的：

$query = "SELECT * FROM populations WHERE username ='{$_SESSION[name]}' AND region_name = 'region'"
$query .= "AND city_name = 'city'"; 
$result = mysqli_query($connection, $query);

$population_value=array(); //Initialize the array so we can just add to it.

while($row = mysqli_fetch_assoc($result)) {
    $population_value[]= intval($row['population_value']); //Just making sure we get a number. 


    echo end($population_value); //We could output the row again, or just grab the last element of the array we added.

}
//Now that the array is fully populated and we've made sure it's only numbers, we output the grand total.
echo array_sum($population_value);

Answer 2

首先，不要用空字符串初始化数组。改为这样做：

$total = array();

或使用新样式：

$total = [ ];

其次，像这样重写 floatval 的东西：

array_push($total, floatval($value));

这应该可以解决它...