php.array_change_key_case()

In PHP, an array is a type of data structure that can hold multiple values or elements under a single variable name. These values can be of any data type such as string, integer, float, or even another array. Each value in an array is identified by a unique index or key, which can be a number or a string.

We can create an array in PHP using various methods and techniques such as the array() function, square bracket [] notation and more. Check the tutorial below to learn more.

https://www.geekbits.io/php-array-function/

In this tutorial, we will learn how we can convert all the keys of an input array to uppercase or lowercase by using the array_change_key_case() function.

Function Syntax

The following shows the definition for the array_change_key_case() method.

array_change_key_case(array $array, int $case = CASE_LOWER): array

Function Parameters

The function accepts two main parameters:

1. array - this refers to the input array on which the function will operate.
2. case - Defines the casing to which the key is converted. Accepted values are
   1. CASE_UPPER - Convert to Uppercase
   2. CASE_LOWER - Convert to Lowercase.

Function Return Value

The function returns an array with all the keys converted to lower case or uppercase. If the input value is not a valid array, the function will return null.

Examples

Let us look at some basic examples of the function usage.

Example 1

The following example demonstrates how to use the function to convert all the keys of an input array to uppercase.

$databases = array(
  "mysql" => 3306,
  "postgresql" => 5432,
  "redis" => 6379,
  "sql server" => 1433
);

$databases_uppercase = array_change_key_case($databases, CASE_UPPER);

print_r($databases_uppercase);

In this case, we use the array_change_key_case() method to convert the keys of the array to uppercase, and store the result in a new array called $databases_uppercase.

Resulting output:

Array
(
    [MYSQL] => 3306
    [POSTGRESQL] => 5432
    [REDIS] => 6379
    [SQL SERVER] => 1433
)

Example 3

Similarly, we can use this function to convert the keys of an input array to lowercase. An example is as shown:

$databases = array(
  "MYSQL" => 3306,
  "POSTGRESQL" => 5432,
  "REDIS" => 6379,
  "SQL SERVER" => 1433
);

$databases_lowercase = array_change_key_case($databases, CASE_LOWER);

print_r($databases_lowercase);

The resulting output is as shown:

Array
(
    [mysql] => 3306
    [postgresql] => 5432
    [redis] => 6379
    [sql server] => 1433
)

Conclusion

In this tutorial, we learned how we can use the array_change_key_case() method to convert the keys of an input array to either lower case or uppercase.

We hope you enjoyed this post.