From PHP7 to PHP8: Comprehensive use of array_key_first() and array_key_last()

PHP 8 is an important update launched by the PHP community. It brings new features and optimizations that greatly improve PHP's performance and development efficiency. Among them, the newly added array_key_first() and array_key_last() functions have also become the focus of many developers. This article will introduce the use of array functions starting from PHP 7, and then discuss them in depth based on the new functions in PHP 8.

1. The use of array functions in PHP 7

In PHP 7, we can operate arrays through a series of functions. The following are several simple array functions:

1. count() function: used to get the number of elements in an array.
2. array_push() function: Add one or more elements to the array.
3. array_pop() function: pops the last element in the array.
4. array_shift() function: pops the first element in the array.
5. array_unshift() function: Adds one or more elements to the beginning of the array.
6. array_flip() function: Swap the keys and values ​​in the array.

We can use these functions to perform a series of regular operations on arrays, such as counting the number of array elements, adding or deleting elements in the array, transforming the structure of the array, etc. These operations can meet the needs of most scenarios, but in some specific cases, we need more sophisticated operations.

For example, in some scenarios, we need to get the first or last key name of the array. Taking getting the first element of an array as an example, if we use the array_keys() function to get the key list of the array, and then use the array_shift() function to pop out the first element, this operation is relatively troublesome. In PHP 7, if we want to get the first key name of the array, we can use the reset() function to achieve it. The specific code is as follows:

$arr = [1, 2, 3, 4, 5];
$first_key = key($arr);

Among them, the key() function returns the element pointed to by the current pointer. key name. In the above code, point the pointer of the $arr array to the position of the first element, and then obtain the key name of the element through the key() function. You can easily obtain the first key name of the array.

2. New array functions in PHP 8

In PHP 8, two new functions, array_key_first() and array_key_last(), are added, which can respectively obtain the first element of the array. key name and the last key name. For example:

$arr = [1 => 'one', 2 => 'two', 3 => 'three'];
$first_key = array_key_first($arr); // 输出 1
$last_key = array_key_last($arr); // 输出 3

The use of these two functions is extremely simple. You can directly pass in the array to be operated without additional operations. This also solves the cumbersome problem of using the key() function when getting the first key name of an array in PHP 7. In addition to the above two functions, many other array functions have been added in PHP 8, which can greatly improve the flexibility and efficiency of array operations.

3. Comprehensive use of array_key_first() and array_key_last()

Although the use of array_key_first() and array_key_last() is very simple, their application in actual development is also very simple. widely. We can get the first element and the last element of the array through these two functions, and then combine them with other functions to perform complex operations.

For example, to add a new element in front of the first element of the array, we can use the array_key_first() function to get the key name of the first element, and then use the array_splice() function to insert it at the specified position in the array. new element. The code is as follows:

$arr = ['one', 'two', 'three'];
$first_key = array_key_first($arr); // 获取第一个元素的键名
array_splice($arr, $first_key, 0, 'zero');
print_r($arr);

The printed array content after execution is:

Array
(
    [0] => zero
    [1] => one
    [2] => two
    [3] => three
)

As you can see, we use the array_key_first() function to get the key name 0 of the first element of the array, and then use The array_splice() function inserts 'zero' into the first position of the $arr array, thereby adding a new element in front of the first element of the array.

In addition, we can also obtain the specified element range in the array through the array_key_first() and array_key_last() functions, for example:

$arr = [1, 2, 3, 4, 5];
$first_key = array_key_first($arr); // 获取第一个元素的键名
$last_key = array_key_last($arr); // 获取最后一个元素的键名
$range = array_slice($arr, $first_key, $last_key - $first_key + 1);
print_r($range);

The array content printed after execution is:

Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
    [4] => 5
)

Get the first and last key names of the array through the array_key_first() and array_key_last() functions, and then use the array_slice() function to take out the array elements within the specified range. You can easily obtain the array elements within the specified range. List of elements. This is very useful for operations such as processing large data arrays, generating pagination, or processing images.

Summary

array_key_first() and array_key_last() Although the two functions are very simple, they are widely used and can be used in combination with multiple other array functions to further improve the flexibility and flexibility of array operations. Performance efficiency. For PHP 8 novices, it is very important to learn and master these two functions.

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