How to resolve the issue of invalid usage of the usort …

If you encounter an invalid use of the usort function, you can try the following solutions:

1. Make sure that the comparison function you pass to the usort function is correct and the return value follows the requirements of the usort function. The comparison function should take two parameters and return an integer value that represents the comparison result of the two elements. If the return value is less than 0, it indicates that the first element should be placed before the second element; if the return value is greater than 0, it indicates that the first element should be placed after the second element; if the return value is equal to 0, it indicates that the two elements are equal.
2. Make sure that your comparison function is correctly passed to the usort function. The comparison function should be passed as the second parameter to the usort function, and the function name should be passed directly, not by reference.
3. Make sure that the array you pass to the usort function is correct and contains the elements you want to sort.
4. Check your comparison function for any syntax or logic errors. You can add some debugging statements in the comparison function to see if it is being called correctly and to verify if the comparison results are accurate.
5. If none of the above methods solve the issue, you may consider using alternative sorting functions or custom sorting algorithms in place of the usort function to meet your needs.