This document discusses different aspects of functions in programming including declaring and calling functions, passing arguments to functions, and returning values from functions. It also covers variable scope. Some key points covered are declaring functions with and without arguments, specifying default values, returning single values or arrays from functions, and understanding variable scope and how it relates to the global and $GLOBALS keywords and array.

1. Functions
Declaring and Calling Functions
Passing Arguments to Functions
Returning Values from Functions
Understanding Variable Scope

2. Declaring and Calling Functions
• Declaring a function
• Calling a function
• Defining functions before or after calling them

3. Declaring Function

4. Calling a function

6. Defining functions before or after
calling them

8. Passing Arguments to Functions
• Declaring a function with an argument
• Specifying a default value
• Defining a two-argument function
• Calling a two-argument function
• Multiple optional arguments
• Changing argument values

9. Declaring a function with an argument

10. Specifying a default value

11. Defining a two-argument function

12. Calling a two-argument function

14. Multiple optional arguments

17. Changing argument values

19. Returning Values from Functions
• Capturing a return value
• Returning a value from a function
• Using a return value in an if( ) statement
• Returning an array from a function
• Using an array returned from a function
• Multiple return statements in a function
• Passing a return value to another function
• Using return values with if( )
• Functions that return true or false
• Assignment and function call inside a test expression

20. Capturing a return value

22. Returning a value from a function

23. Using a return value in an if( )
statement

25. Returning an array from a function

26. Using an array returned from a
function

28. Multiple return statements in a
function

29. Passing a return value to another
function

32. Using return values with if( )

34. Functions that return true or false

37. Assignment and function call inside a
test expression

40. Understanding Variable Scope
• Variable scope
• The $GLOBALS array
• Modifying a variable with $GLOBALS
• The global keyword

41. Variable scope

43. The $GLOBALS array

45. Modifying a variable with $GLOBALS

47. The global keyword