Use the array function array_key_first() in PHP8 to easily get the first key name of the array

PHP is a popular server-side scripting language widely used for web development. Arrays are one of the most commonly used structures in PHP, providing an ordered, repeatable collection of data. Each element in the array is represented by a key-value pair, where the key is unique and the value can be any type of data.

PHP 8 is the latest version of the PHP language, officially released in November 2020. This version brings many new features and improvements, one of which is the array_key_first() function. In this post, we'll introduce this new function and how you can use it to easily get the first key of an array.

array_key_first() function

In PHP 8, array_key_first() is a new array function. It returns the name of the first key in the array, or NULL if the array is empty. This function can only be used with associative arrays (i.e. arrays that use strings as keys), not indexed arrays.

The following is the basic syntax of the array_key_first() function:

array_key_first(array $array): mixed

The parameter $array is the array to obtain the key name. The function returns the name of the first key, or NULL if the array is empty.

The following is a simple example using the array_key_first() function:

$array = ['a' => 1, 'b' => 2, 'c' => 3];
echo array_key_first($array); // 输出 'a'

In the above example, we create an associative array containing three elements and obtain it using the array_key_first() function The name of the first key. The function returns the string 'a', which we output to the screen using the echo statement.

Use array_key_first() to get the first key of the array

The array_key_first() function provides a simple way to get the first key of the array. Before PHP 8, you usually needed to use the array_keys() function to get all the keys of the array, and then get the first key. This approach is a bit clunky and may not perform well on large arrays.

The following is an example of using the array_keys() function and the traditional method to get the first key name of the array:

$array = ['a' => 1, 'b' => 2, 'c' => 3];

// 使用array_keys()函数
$keys = array_keys($array);
$first_key = $keys[0];
echo $first_key; // 输出 'a'

// 传统方法
reset($array);
$first_key = key($array);
echo $first_key; // 输出 'a'

In both methods, we can get the first key name of the array key name. In the first method, we use the array_keys() function to get all the keys of the array and store the result in the $keys variable. Then, we use the first element of the $keys array to get the first key name. In the second method, we use the reset() function to reset the array pointer to the first element, and then use the key() function to get the first key name.

Using the array_key_first() function, this process becomes very simple:

$array = ['a' => 1, 'b' => 2, 'c' => 3];
$first_key = array_key_first($array);
echo $first_key; // 输出 'a'

In this example, we use the array_key_first() function to directly obtain the first key name of the array, and the code is streamlined. Easier to read.

Notes

When using the array_key_first() function, you need to pay attention to the following points:

• The array_key_first() function can only be used for associative arrays and cannot be used in the index array.
• If the array is empty, NULL is returned.
• Since array_key_first() was introduced in PHP 8, it can only be used in PHP 8 or higher.

Summary

The array_key_first() function is a new array function in PHP 8. It provides a convenient way to get the first key name of the array. Using the array_key_first() function, we avoid the redundant code when using the traditional method to obtain the first key name, and the code looks more concise and readable.

Although this function is not necessarily necessary for most developers, in some special cases, it can make the code simpler and easier to maintain. If you are a PHP developer and using PHP 8 or higher, the array_key_first() function is a useful function worth knowing.

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