Call to undefined function array_column()

The array_column() function is only available in php 5.5 or higher. If it's not available, add in your own version. This is the original article:

http://stackoverflow.com/questions/27422640/alternate-to-array-column

if (! function_exists('array_column')) {
    function array_column(array $input, $columnKey, $indexKey = null) {
        $array = array();
        foreach ($input as $value) {
            if ( ! isset($value[$columnKey])) {
                trigger_error("Key \"$columnKey\" does not exist in array");
                return false;
            }
            if (is_null($indexKey)) {
                $array[] = $value[$columnKey];
            }
            else {
                if ( ! isset($value[$indexKey])) {
                    trigger_error("Key \"$indexKey\" does not exist in array");
                    return false;
                }
                if ( ! is_scalar($value[$indexKey])) {
                    trigger_error("Key \"$indexKey\" does not contain scalar value");
                    return false;
                }
                $array[$value[$indexKey]] = $value[$columnKey];
            }
        }
        return $array;
    }
}