PHP function introduction—array_keys(): Returns an array of all key names in the array

PHP function introduction—array_keys(): Returns an array of all key names in the array

In PHP, there are many powerful array processing functions, among which array_keys() is a very useful function. The array_keys() function returns a new array of all keys in the given array. This article will introduce the usage of array_keys() function, with code examples to better understand how it works.

The syntax of the array_keys() function is as follows:
array_keys ( array $array [, mixed $search_value = null [, bool $strict = false ]] ) : array

Parameter introduction:

• $array: The array whose key name needs to be obtained.
• $search_value (optional): If this parameter is specified, only key names whose corresponding value is equal to $search_value will be returned.
• $strict (optional): If set to true, strict comparison is used (types and values ​​are equal).

The following are some examples of using the array_keys() function:

Example 1:

<?php
// 创建一个数组
$fruits = array("apple", "banana", "orange", "apple", "grape");
// 获取数组中的所有键名
$keys = array_keys($fruits);
// 打印结果
print_r($keys);
?>

Output results:

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

In the above example , an array containing multiple identical elements is created. Use the array_keys() function to get all the key names in the array and store the results in a new array $keys. Finally, the contents of the $keys array are printed out through the print_r() function.

Example 2:

<?php
// 创建一个关联数组
$student_scores = array("Mike" => 85, "John" => 92, "Sarah" => 78);
// 获取数组中的所有键名
$keys = array_keys($student_scores);
// 打印结果
print_r($keys);
?>

Output result:

Array
(
    [0] => Mike
    [1] => John
    [2] => Sarah
)

In this example, we create an associative array containing the names of students and their scores. By using the array_keys() function, we get all the key names in the array and store the results in the array $keys. Finally, the contents of the $keys array are printed out through the print_r() function.

Example 3:

<?php
// 创建一个包含多维数组的数组
$students = array(
    array("name" => "Mike", "age" => 20),
    array("name" => "John", "age" => 22),
    array("name" => "Sarah", "age" => 19)
);
// 获取所有学生姓名的键名
$names = array_keys($students[0]);
// 打印结果
print_r($names);
?>

Output result:

Array
(
    [0] => name
    [1] => age
)

In this example, we create a multi-dimensional array containing multiple student information. By using the array_keys() function, we get all the key names of the first student in the array and store the results in the $names array. Finally, the contents of the $names array are printed out through the print_r() function.

Through the above example, we can see the power of the array_keys() function. It can easily get all the key names in an array, whether it is an index array, an associative array, or even a multi-dimensional array.

Summary:
In PHP, the array_keys() function is a very useful function. It returns a new array of all keys in the given array, whether the array is an indexed array, an associative array, or a multidimensional array. The concise syntax and flexibility of the array_keys() function make it very practical in actual development.

I hope this article will help everyone understand and use the array_keys() function. Thanks for reading!

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