Multidimensional array implode (PHP >= 5.4)

multiimplode.php

/**
 * Join array elements with a string.
 * This method works with multidimensional arrays.
 *
 * @param string|array $glue the string for the array to be joined with or 
 * the array itself if $array is null
 * @param array|null $array array to implode or null if array is provided as 
 * first parameter.
 * @return string imploded array
 * @throws \yii\base\InvalidParamException
 */
public static function implode($glue, $array = null)
{
    if ($array === null) {
        $array = $glue;
        $glue = '';
    }
    if (!is_array($array)) {
        throw new \yii\base\InvalidParamException('You must provide an array to implode.');
    }
    if (!is_string($glue)) {
        throw new \yii\base\InvalidParamException('Parameter $glue must be a string.');
    }
    $flat = [];
    array_walk_recursive($array, function ($element) use (&$flat) { $flat[] = $element; });
        
    return implode($glue, $flat);
}

great! throw new \yii\base\InvalidParamException may better