PHP function introduction: array_key_first() function

Introduction to PHP functions: array_key_first() function

PHP is a widely used server-side scripting language, and functions are an integral part of PHP programming. In the PHP function library, the array_key_first() function is a practical function introduced in PHP version 7.3. Its function is to get the first key name of the array.

The syntax of the array_key_first() function is as follows:

array_key_first(array $array): mixed

Among them, $array represents the array to be operated on. This function returns the first key of the array. If the array is empty, NULL is returned.

In order to better understand the usage and function of the array_key_first() function, a specific code example is given below:

$students = array("Tom" => 18, "Jerry" => 19, "Alice" => 20);

$first_key = array_key_first($students);

echo "第一个学生的姓名是：".$first_key;

In the above example, we define an array $students, key The first name corresponds to the student's name, and the key value corresponds to the student's age. Then, we use the array_key_first() function to get the first key name of the array and save it in the variable $first_key. Finally, we output the results to the screen through the echo statement. In the above example, the output would be "The first student's name is: Tom".

It should be noted that the array_key_first() function is only available in PHP 7.3 and above. If your PHP version is lower, you cannot use this function. In older versions of PHP, you can use the array_keys() function to retrieve all the keys of an array and take the first key from it.

$students = array("Tom" => 18, "Jerry" => 19, "Alice" => 20);

$keys = array_keys($students);
$first_key = $keys[0];

echo "第一个学生的姓名是：".$first_key;

The above code first obtains all the key names of the array $students through the array_keys() function and saves them in the $keys array. Then, we retrieve the first key name through the $keys array, save it in $first_key, and output the result.

Summary:
The array_key_first() function is a practical function introduced in PHP 7.3 version, used to obtain the first key name of the array. If you have an older version of PHP, you can use the array_keys() function to accomplish the same functionality. No matter which method is used, we can flexibly obtain the first key name of the array, thereby conveniently manipulating the data in the array.

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