I don't understand the sorting of array custom functions. Can any expert help me with the answer? Thank you.

Question

Who can tell me what the values ​​of these two parameters are and where they come from. Why can this function be sorted when written like this? I have been thinking about it all night and I don’t understand.

Answer 1

$var1 and $var2 are two adjacent key values ​​​​in the $arr array. Each time, the two adjacent key values ​​​​are compared, that is, key value 1 is first compared with key value 2, and after the comparison, the key value is 2 is compared with key value 3, and so on, all the way to the end of the array.

Answer 2

This is just a built-in function.

Answer 3

usort is a built-in function in PHP. usort() allows users to sort arrays using custom functions.

usort compares two elements each time and obtains the return value for sorting. 0, -1, and 1 represent equal, less than, and greater respectively.

Answer 4

    

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