This function implements a comparison algorithm that orders alphanumeric strings in the way a human being would, this is described as a "natural ordering". An example of the difference between this algorithm and the regular computer string sorting algorithms (used in strcmp()) can be seen below:
Standard string comparison Array (  => img1.png  => img10.png  => img12.png  => img2.png ) Natural order string comparison Array (  => img1.png  => img2.png  => img10.png  => img12.png )
Similar to other string comparison functions, this one returns < 0 if str1 is less than str2; > 0 if str1 is greater than str2, and 0 if they are equal.
Note that this comparison is case sensitive.