How to use the array_sum function in PHP to calculate the sum of elements in a column of a two-dimensional array

In PHP programming, the array_sum function is a very practical function that can calculate the sum of all elements in an array. However, when we need to calculate the sum of a column of elements in a two-dimensional array, we may encounter some trouble. This article will introduce how to use the array_sum function in PHP to calculate the sum of elements in a column of a two-dimensional array.

First of all, we need to understand the concept of two-dimensional array. A two-dimensional array is an array containing multiple arrays, which can be regarded as a table. Each array represents a row of the table, and each element represents the value of a cell in the table. For example, the following two-dimensional array:

$array = array(
    array('a', 1, 2, 3),
    array('b', 4, 5, 6),
    array('c', 7, 8, 9)
);

This two-dimensional array has three arrays, each containing four elements. The first element represents the identifier of this row, and the next three elements represent the data of this row.

Suppose we now need to calculate the sum of the elements in the second column of this two-dimensional array (that is, the sum of the three numbers 1, 4, and 7), we can use the following method:

$sum = 0; // 初始化总和为0
foreach ($array as $row) { // 遍历每一行
    $sum += $row[1]; // 把这一行的第二个元素加到总和中
}
echo $sum; // 输出结果

This method first initializes the sum to 0, then traverses each row in the array, and adds the second element of this row to the sum. Finally, output the sum.

However, if there are multiple columns of data in the two-dimensional array, we need to manually specify the columns to be calculated. If we want to calculate the sum of the third column of data, we need to change $row[1] in the code to $row[2]. A clear coding style can greatly reduce the probability of program errors. However, if there are a large number of columns in the array, manual calculation will be more troublesome. In this case, we can use the array_column function to easily extract the columns that need to be calculated.

$column = array_column($array, 2); // 提取出第三列数据
$sum = array_sum($column); // 对提取出的列进行总和计算
echo $sum; // 输出结果

This method first uses the array_column function to extract the third column of data in the array, and then uses the array_sum function to calculate the sum. In this way, we can easily calculate the sum of any column of data.

To summarize, we have two methods for calculating the sum of a column of data in a two-dimensional array. The first method is to traverse the array and manually extract each column of data to calculate the sum; the second method is to use the array_column function to extract the columns that need to be calculated, and then use the array_sum function to calculate the sum. The former is suitable for situations where there are fewer columns, while the latter is suitable for situations where there are many columns, and is more concise and convenient.

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