Helper to convert PascalCase strings or arrays of strings into snake_case format

PascalCaseToSnakeCaseConverter.php

<?php

/**
 * Convert PascalCase string or array values to snake_case.
 *
 * @param  array|string  $input
 * @return array|string
 */
function pascalToSnakeCase(array|string $input): array|string
{
    // If the input is an array, recursively call this function for each element
    if (is_array($input)) {
        return array_map('pascalToSnakeCase', $input);
    }

    // Convert the input string from PascalCase to snake_case
    return strtolower(preg_replace('/(?<!^)([A-Z][a-z]|(?<=[a-z])[A-Z])/', '_$1', $input));
}


// Example usage
$input = [
    'HelloWorld',
    'ANOTHERExampleString',
    ['NestedStringOne', 'NESTEDStringTwo'],
    ['NestedStringThree', 'NestedStringFour']
];

$output = pascalToSnakeCase($input);

print_r($output);

// Output
Array
(
    [0] => hello_world
    [1] => another_example_string
    [2] => Array
        (
            [0] => nested_string_one
            [1] => nested_string_two
        )

    [3] => Array
        (
            [0] => nested_string_three
            [1] => nested_string_four
        )

)