php list each array conversion

The list() function and each() function in PHP are very practical array functions. Using these two functions together makes it easy to perform conversion operations on arrays. This article will introduce how to use the list() function and each() function to convert arrays.

1. Introduction to list() function

The list() function is a very simple and practical function provided by PHP. It can assign the values ​​in an array to a set of variables. Specifically, the list() function can assign the value of each element in the array to the variable in parentheses in order. For example:

list($var1, $var2, $var3) = array("apple", "banana", "cherry");
echo $var1; //输出：apple
echo $var2; //输出：banana
echo $var3; //输出：cherry

In this way, we can assign the values ​​​​in the array to variables in sequence.

2. Introduction to each() function

Theeach() function can be used to obtain the key-value pairs in the array and move the pointer to the next position in the array. The each() function can be used in conjunction with the list() function to easily convert arrays.

each() function returns an array containing the following four key-value pairs:

• key: the key of the current element
• value: the key of the current element Value
• 0: The key of the current element (same as the key key)
• 1: The value of the current element (the same as the value key)

For example:

$array = array("apple"=>"red", "banana"=>"yellow", "cherry"=>"red");
$element = each($array);
print_r($element);

The output results are as follows:

Array
(
    [1] => red
    [value] => red
    [0] => apple
    [key] => apple
)

In this example, the each() function first obtains the array element with the key name "apple". It then returns an array containing the key name, value, and two numeric keys.

3. Use functions in combination

Now we have understood the basic usage of list() and each() functions. Next, let's look at an example of using these two functions together. Suppose we have an array and we need to convert it into a new array that only contains the keys and values ​​corresponding to the odd indexes of the original array. We can follow the following steps to get the desired result:

//原始数组
$array = array("a", "b", "c", "d", "e");
//定义一个新的空数组
$new_array = array();
//使用each()函数获取奇数索引的键值对，并使用list()函数将其转换为变量
while(list($key, $value) = each($array)) {
    //如果键值为奇数，则添加到新数组中
    if($key % 2 != 0) {
        $new_array[$key] = $value;
    }
}
//打印结果
print_r($new_array);

The running result is:

Array
(
    [1] => b
    [3] => d
)

In the above code, we traverse each element in the original array and convert it into a key value pair. If the key is an odd number, add it to a new array. Finally, we use the print_r() function to output the results.

By combining the list() function and each() function, we can easily perform conversion operations on arrays. If you want to learn more about these functions, you can refer to the detailed introduction of these functions in the official PHP documentation.

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