The range() function is an inbuilt function in PHP which is used to create an array of elements of any kind such as integer, alphabets within a given range(from low to high) i.e, list’s first element is considered as low and last one is considered as high.
An array is a collection of objects that contain a group of variables stored under the same name. All the elements belong to the same data type, i.e. string, integers, or lists. Keys are unique in the case of both indexed and associative arrays.
The main difference between isset() and array_key_exists() function is that the array_key_exists() function will definitely tells if a key exists in an array.
array_reduce() Method: As the name suggests, an array_reduce() function reduces the array to a single value by performing the given operation. The array_reduce() applies the callback function to the elements of the array and gives output as a single value.