编写一个Python函数，输入一段文本，输出其中出现次数最多的单词及其出现次数。
text = "Hello world, hello python world. Python is a popular language."
```python
def max_word_count(text):
    words = text.lower().split()   # 将文本转换为小写，并按空格分割单词
    word_count = {}   # 创建空字典，记录单词出现次数
    for word in words:
        if word in word_count:
            word_count[word] += 1
        else:
            word_count[word] = 1
    max_word = max(word_count, key=word_count.get)   # 获取出现次数最多的单词
    return max_word, word_count[max_word]   # 返回出现次数最多的单词及其出现次数
```

使用示例：
```python
text = "Hello world, hello python world. Python is a popular language."
print(max_word_count(text))   # 输出：('hello', 2)
```