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Unit 4: Functions

4.8 Summary Notes

• A function call is a piece of code that tells your program to “call in” the built-in function
whenever you need it. The second type of function is the user defined function. These are
the functions that you write yourself.

• Unlike PHP variable names, PHP function names are case insensitive. It is however
recommended to remain rigorous when naming and calling any PHP object.
• The function takes two arguments, $left and $right. Using the concatenation operator, the
function creates a combined string in the variable$combined_string.
• The variables used in PHP functions can be of three types: locals, globals and statics. Any
variable defined inside a function is by default limited to the local function scope, is available
only in the code within that function.
• PHP supports the concept of variable functions. This means that if a variable name has
parentheses appended to it, PHP will look for a function with the same name as whatever
the variable evaluates to, and will attempt to execute it.

4.9 Keywords

Default parameters: Default parameters enable you to specify a default value for function
parameters that are not passed to the function during the function call.
Function: A function call is a piece of code that tells your program to “call in” the built-in function
whenever you need it.
Global variables: A global variable can be accessed in any part of the program. If you want to
use inside a function a variable defined outside it, that variable must be explicitly declared to be
global in the function.
Static variables: A static variable exists only in a local function scope, but it does not lose its value
when program execution leaves this scope.

1. Develop a PHP program to add two numbers with the help of function.
2. Create a PHP program to concatenate two strings.

4.10 Review Questions

1. What do you mean by function? How does it define in PHP?

2. How do we call a function in PHP?
3. Explain the user defined function with example.
4. What is the variable scope in PHP?
5. Differentiate between local and global scope of variables.

6. What is the function parameters used in PHP?
7. Differentiate between pass by value and pass by reference parameters.
8. Explain the return values in PHP.

9. What are the variable functions?
10. How many categories of PHP functions are there?

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