Introduction to how to use the PHP array_change_key_case() function

In PHP programming, array is a frequently used data type. There are also quite a few array operation functions, including the array_change_key_case() function. This function can convert the case of key names in the array to facilitate our data processing. This article will introduce how to use the array_change_key_case() function in PHP.

1. Function syntax and parameters

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

array array_change_key_case ( array $array [, int $case = CASE_LOWER ] )

In this syntax,

• array: required. Array to be converted.

• case: Optional. There are two options for the case format of the key name after conversion:

  • CASE_UPPER: Convert to uppercase format.
  • CASE_LOWER: Convert to lowercase format. The default value is CASE_LOWER.

2. Example demonstration

The following uses some examples to demonstrate the use of the array_change_key_case() function.

1. Convert the array key names to lowercase

The following is a simple array, in which we convert the key names to lowercase format:

<?php 
   $array = array(
      "name" => "Tom",
      "ID" => 1001,
      "AGE" => 25,
   );
   
   $array_lower = array_change_key_case($array, CASE_LOWER);
   print_r($array_lower);
?>

The output results are as follows:

Array ( [name] => Tom [id] => 1001 [age] => 25 )

In the above code, we convert the key names of the $array array into lowercase and save the results in the $array_lower array middle. The output results are visible, and the key names have been changed to lowercase format.

2. Convert the array key names to uppercase

In the following example, we convert the array key names to uppercase format:

<?php 
   $array = array(
      "name" => "Jack",
      "Age" => 22,
      "ID" => 1002,
   );
   
   $array_upper = array_change_key_case($array, CASE_UPPER);
   print_r($array_upper);
?>

The output results are as follows ：

Array ( [NAME] => Jack [AGE] => 22 [ID] => 1002 )

In the above code, we convert the key names in the $array array into uppercase format, and save the results in the $array_upper array . As you can see from the output, the key names have been changed to uppercase format.

3. Notes

• If there are two or more key names in the array with the same case after conversion, the subsequent key names will overwrite the previous key names;
• If there are non-string key names in the array, they will be automatically converted to string format for conversion.

4. Summary

This article introduces how to use the array_change_key_case() function in PHP, which can convert the case of the key names in the array. This function can facilitate our data processing, the code is simple and easy to learn, and has certain practicality. At the same time, we also need to pay attention to relevant precautions when using it.

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