lib/IniModifierArray.php
public function offsetSet($offset, $value)
    {
        $value = $this->checkValue('A given value', $value);
        if (is_null($offset)) {
            $this->modifiers[] = $value;
        } else {
            $this->modifiers[$offset] = $value;
        }
        $this->setReversedArray();
    }
public function offsetSet($offset, $value)
    {
        $value = $this->checkValue('A given value', $value);
        if (is_null($offset)) {
            $this->modifiers[] = $value;
        } else {
            $this->modifiers[$offset] = $value;
        }
        $this->setReversedArray();
    }
---------------------------------------------- \ArrayAccess