Array functions in PHP8: new application method of array_key_first()

On November 26, 2020, the PHP8 version was officially released, which brought many new features and bug fixes. One of the things that has attracted the attention of many developers is the new application method of the array function array_key_first().

In the past, we might use the array_shift() function to get the key name of the first element of the array. But there is a problem with this method, that is, NULL will be returned when the array is empty. In PHP8, we can use the array_key_first() function to directly obtain the first key name. The following is its syntax:

array_key_first(array $array): mixed

It accepts an array parameter and returns the first key name. If the array is empty, NULL is returned.

Now, let’s take a look at the new application method of array_key_first().

1. Get the key name of the first level of a multi-dimensional array

In PHP8, use array_key_first() to directly get the key name of the first level of a multi-dimensional array. For the following example array:

$oldArr = array( 'fruit' => array( 'apple' => 'red', 'banana' => 'yellow' ), 'flower' => array( 'rose' => 'red', 'sunflower' => 'yellow' ) );

We can use the following code to get the first key name (i.e. 'fruit'):

$firstKey = array_key_first($oldArr);

If we use the traditional method to get the first key name, It may take a few more lines of code:

reset($oldArr); $firstKey = key($oldArr);

2. Get the first element when traversing an array

When traversing an array, we usually need to get the first element and perform certain operations. In PHP8, we can use the array_key_first() function to achieve this requirement. Here is a sample code:

foreach ($oldArr as $key => $value) { if ($key === array_key_first($oldArr)) { // 处理第一个元素 } // 其他元素的处理 }

In the above code, we process each element and if it is the first element, we will perform a specific operation. If you use the traditional method, you need to use a counter or marker variable to achieve the same functionality.

3. Quickly get the first element in a variable

Sometimes we need to get the first element from a variable, and this variable may be an array or Other types of data. In PHP8, we can easily use the array_key_first() function to achieve this requirement. The following is a sample code:

function getFirstElement($var) { if (is_array($var)) { return $var[array_key_first($var)]; } else { return $var; // 如果$var不是数组，则直接返回 } }

In the above code, we define a function called getFirstElement, which accepts a parameter $var and gets the first element from it.

Summary

array_key_first() is a new array function in PHP8 and has many new application methods. We can use it to get the first level key name of a multi-dimensional array, get the first element when traversing the array, and quickly get the first element in a variable. These application methods can help us write code faster and improve the readability and maintainability of the code.

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