Are there any best practices or recommended functions in PHP for extending the values of an array without losing existing data?

When extending the values of an array in PHP without losing existing data, one common approach is to use the `array_merge` function. This function allows you to merge two or more arrays together while preserving the keys of the original arrays. By using `array_merge`, you can add new values to an array without overwriting any existing data.

// Existing array
$existingArray = array('key1' => 'value1', 'key2' => 'value2');

// New values to add
$newValues = array('key3' => 'value3', 'key4' => 'value4');

// Extend the existing array without losing data
$extendedArray = array_merge($existingArray, $newValues);

// Output the extended array
print_r($extendedArray);