How to sum based on array key names in php

In PHP, array is a very convenient data structure that can be used to save various types of data, including integers, strings, floating point numbers, etc. When we need to sum the values ​​in an array, we often face a problem, that is, how to sum based on the array keys. This article will introduce how to use PHP to achieve this operation.

First of all, we need to understand the two keywords in PHP: array and foreach. Array is used to create an array, while foreach is used to iterate through an array and perform some operation on each element in it. For example, we can use the following code to create an array containing integers:

$arr = array(
    "a" => 1,
    "b" => 2,
    "c" => 3
);

The above code creates an array containing three elements, and the keys of the array are "a", "b" and "c" ", the corresponding values ​​are 1, 2 and 3 respectively. We can use foreach to iterate through this array and sum the elements. The code is as follows:

$total = 0;
foreach ($arr as $key => $value) {
    $total += $value;
}
echo $total;

The above code will traverse the array $arr and operate on each element in it. In each loop, the variable $key will save the key name of the current element, and the variable $value will save the value of the current element. In this example, we add the value of $value to $total, thereby implementing the sum operation. Finally, we use the echo statement to output the value of $total, which is the sum of all elements in the array.

However, the above code only sums the values ​​in the array. If we need to sum based on the array key name, how should we do it? At this time, we can use a little trick in PHP: use the list function to store the key names and values ​​of the array elements into two variables respectively. Specifically, we can use the following code to achieve this operation:

$total = 0;
foreach ($arr as $key => $value) {
    list($k, $num) = explode('_', $key);
    $total += $num;
}
echo $total;

In the above code, we store the key name of the array element in the $k variable and the value in the $num variable. We use the explode function to split the key name into two parts according to "_", and then store the value of the second part into the $num variable, thus realizing the sum operation based on the array key name.

In addition, we can also use the array_sum function to sum the values ​​in the array. The array_sum function accepts an array as a parameter and returns the sum of the values ​​in the array. For example, we can use the following code to sum the elements in the array $arr:

$total = array_sum($arr);
echo $total;

The above code will sum all the elements in the array $arr and output the result to the screen.

In summary, PHP provides a wealth of functions and syntax for operating arrays, and we can choose the most appropriate method for implementation based on specific needs. Whether we are summing based on array values ​​or key names, we can use the foreach statement and array functions to achieve it. I hope this article will help you understand the operation of PHP arrays.

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