We covered a lot in this lesson! Great job. Take a second to review everything you learned:

• Arrays are ordered collections of data that are a type of data structure fundamental to computer science.
• In PHP, we refer to this data structure as ordered arrays.
• The location of an element in an array is known as its index.
• The elements in an ordered array are arranged in ascending numerical order starting with index zero.
• We can construct ordered arrays with a built-in PHP function: array().
• We can construct ordered arrays with short array syntax, e.g. [1,2,3].
• We can print arrays using the built-in print_r() function or by converting them into strings using the implode() function.
• We use square brackets ([]) to access elements in an array by their index.
• We can add elements to the end of an array by appending square brackets ([]) to an array variable name and assigning the value with the assignment operator (=).
• We can change elements in an array using array indexing and the assignment operator.
• The array_pop() function removes the last element of an array.
• The array_push() function adds elements to the end of an array.
• The array_shift() function removes the first element of an array.
• The array_unshift() function adds elements to the beginning of the array.
• We can use chained square brackets ([]) to access and change elements within a nested array.