1. ITC 240: Web Application Programming
Subhash Prajapati
04/23/15

2. Review Array - variable type that can hold many values at a time
Indexed Array - arrays with numeric index
Associative Array - arrays with named keys
Multidimentional Array - arrays within the array

3. Today
Array Exercise
Loops

4. Review Exercise: 6.1
Create students array that would include all the students name in a class
[Numeric Indexed Array]
Create a states array with state abbreviations as keys
[Associative Array]
Create students array with marks on different subjects
[Multidimensional Array]

5. unset()/isset()
These are two PHP built-in functions to do following: isset() - check whether a variable is set or not (od ) unset() – destroys the variable We can destroy/delete the array element like this: unset ($myArray[2])

6. Loop
We can alter the flow of control using either conditionals or loops
Loops: execute a statement(s) over and over.
Usually contains:
- a start condition
- a break condition
- change in each iteration

7. while loop
loops through a block of code as long as the specified condition is true

8. while loop
Syntax: while (condition) { // code block to be executed }

9. while loop example
Following loop will iterate 4 times $counter = 1; while ($counter<5) { echo “The counter is: ” . $counter.”<br>”; $counter++; }

10. Quiz
What happens to following code $counter = 0; while ($counter < 1) { echo “The counter is: ” . $counter.”<br>”; $counter--; }

11. Class Exercise 6.2
Write a program with while loop, which would print following table of squares (styling not required)
Number
Square Value 1 2 4 3 9 16 5 25 6 36 7 49 8 64 81 10
100

12. while loop alternative syntax
while (expression): // statements goes here endwhile; eg: $i = 0; while ($i<10): echo $i; $i++;

13. do .. while loop
loops through a block of code once, and then repeats the loop for specified condition is true

14. do .. while loop
Syntax: do { // code block to be executed } while (condition);

15. do .. while loop
do { do_work(); } while (condition); is equivalent to while (condition) { }

16. while vs do .. while loop
The difference between do-while and while is that do-while evaluates its expression at the bottom of the loop instead of the top. Therefore, the statements within the do block are always executed at least once.

17. while example scenario
Consider a program which writes some text in a file until file size becomes 5MB. We can use while loop in this scenario like this. while(IsFileSizeLessThan5MB()) { WriteMoreData (); }

18. do .. while example scenario
Let's consider another scenario where we want to take an integer input from user until user has entered a positive number. In this case we will use a do-while loop like this. do { TakeInputFromUser(); } while ($input < 0);

19. Class Exercise 5.3
Cumulative Sum: write a method (function) with a while loop that computes the sum of first n positive integer.
for eg: if you pass 5, it will give 15 (sum of )
hints:
Declare a function which will take one argument, the function will return the sum
Inside the function, write a while loop which will iterate n number of time (n= number passed in that function)
Inside the while loop, do the addition of the numbers