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CHAPTER 5 • ARRAYSwww.it-ebooks.info$states = array("Delaware", "Pennsylvania", "New Jersey");print_r(array_reverse($states));// Array ( [0] => New Jersey [1] => Pennsylvania [2] => Delaware )Contrast this behavior with that resulting from enabling preserve_keys:$states = array("Delaware", "Pennsylvania", "New Jersey");print_r(array_reverse($states,1));// Array ( [2] => New Jersey [1] => Pennsylvania [0] => Delaware )Arrays with associative keys are not affected by preserve_keys; key mappings are always preserved inthis case.Flipping Array Keys and ValuesThe array_flip() function reverses the roles of the keys and their corresponding values in an array. Itsprototype follows:array array_flip(array array)An example follows:$state = array("Delaware", "Pennsylvania", "New Jersey");$state = array_flip($state);print_r($state);This example returns the following:Array ( [Delaware] => 0 [Pennsylvania] => 1 [New Jersey] => 2 )Sorting an ArrayThe sort() function sorts an array, ordering elements from lowest to highest value. Its prototype follows:void sort(array array [, int sort_flags])The sort() function doesn’t return the sorted array. Instead, it sorts the array “in place,” returningnothing, regardless of outcome. The optional sort_flags parameter modifies the function’s defaultbehavior in accordance with its assigned value:SORT_NUMERIC: Sorts items numerically. This is useful when sorting integers or floats.SORT_REGULAR: Sorts items by their ASCII value. This means that B will come before a, forinstance. A quick search online produces several ASCII tables, so one isn’t reproducedin this book.SORT_STRING: Sorts items in a fashion that better corresponds with how a human mightperceive the correct order. See natsort() for more information about this matter,introduced later in this section.120