PHP Functions

Programmer-defined functions

• Despite PHP’s many built-in functions, there will be many times you will want to create your own functions.

• Reasons for creating functions:
• reusable code
• easier to manage and debug code which has been broken down into smaller parts

• Functions:
• are defined using the function keyword
• names should be meaningful, but must begin with a letter or underscore, and then may contain letters, numbers, or underscores
• names are case insensitive
• may take arguments, which are limited in scope – you can use any variable name, but by practice, name them differently than any global variables
• when a function ends, it can give a “reply” to the code that called it by returning a value – use the return keyword

The syntax for creating your own functions is:

function function_name( ) {

      statements;

} 

To call the function use the function name.

Arguments

• PHP functions can take arguments or parameters. 
• You can create functions to take as many arguments as necessary, but they must be passed in the proper order.
•  Failure to send the correct number of variables will result in an error.
• use return statement to return a value

Default Arguments

• setting a default value for an argument makes it optional
• passed values overwrite the default
• place default arguments last in function definition

• You can set as many default values as you need, as long as you place them last in the function definition. Required arguments must come first.

Variable scope

• The scope of a variable used in a function is local to the function by default
• To create a global variable use global keyword