Recursive trim() function to handle arrays and objects

Question

I have come up with a recursive function which applies trim() recursively to all string members of an array/object.

I don't have any specific quandaries about my code so I am receptive to all feedback.

My goal is maximum compatibility for all PHP versions: past, present, and future.

<?php
/**
 * trim_r
 * 
 * Recursively trim an array's or object's string values
 * Preserves all non-string values
 * 
 * @access  public
 * @param   mixed
 * @param   mixed
 * @return  mixed
 */
function &trim_r( &$o, $character_mask = null )
{
    // Only apply trim() to strings
    if( is_string( $o ) )
    {
        // Respect the $character_mask; cannot pass null as 2nd parameter for some HHVM versions
        $o = ( $character_mask === null ? trim( $o ) : trim( $o, $character_mask ) );
    }
    elseif( is_array( $o ) || is_object( $o ) )
    {
        // Loop this array/object and apply trim_r() to its members
        foreach( $o as &$v )
        {
            trim_r( $v );
        }
    }

    // Supply this just in case the invoker wishes to receive result as a reference
    return $o;
}

Answer 1

Avoid if-else nesting to keep things flat. Return inside the first if is enough to do so.

---

I added is_iterable() so this function can handle more types than just array

/**
 * trim_r
 *
 * Recursively trim an array's or object's string values
 * Preserves all non-string values
 *
 * @access  public
 * @param   mixed
 * @param   mixed
 * @return  mixed
 */
function &trim_r( &$o, $character_mask = null )
{

    // Only apply trim() to strings
    if( is_string( $o ) )
    {
        // Respect the $character_mask; cannot pass null as 2nd parameter for some HHVM versions
        $o = trim( $o, $character_mask ?? " \t\n\r\0\x0B" );
        return $o;
    }

    if( is_iterable($o) || is_object( $o ) )
    {
        // Loop this array/object and apply trim_r() to its members
        foreach( $o as &$v )
        {
            trim_r( $v );
        }

    }

    // Supply this just in case the invoker wishes to receive result as a reference
    return $o;
}