任何人都可以解释，为什么我的排序不能正常工作？ [关闭]

I wanted to use usort() function to sort array by it's values' lengths. Here is my function:

$max_min_length = function ($a, $b) {

if (strlen($a) > strlen(b))
    return 1;
elseif (strlen($a) < strlen(b))
    return -1;
else
    return 0;
};

$array = ["abcd","abc","de","hjjj","g","wer"];
usort($array, $max_min_length);
print_r($array);

The output is:

Array ( [0] => g [1] => abcd [2] => abc [3] => hjjj [4] => de [5] => wer )

I cannot understand, why it doesn't sort properly. Am I missing something? I've looked at PHP: Sort an array by the length of its values? and their solutions work just fine. I just want to know, why does this happen? Thanks in advance.

You have typo for "b" without "$"

replace code with:

if (strlen($a) > strlen($b))
    return 1;
elseif (strlen($a) < strlen($b))
    return -1;
else
    return 0;
};

After it your code will work fine :)