Zend Php 5 Certification - Functions

Front 1

What is a function

Back 1

A piece of code that has the ability to be called over and over again.

Hint 1

Page 37

Front 2

How do you create a new function in PHP?

Back 2

Use the keyword function, followed by an identifier.

Example:

function myFunction()
{
}

Hint 2

Page 37

Front 3

Are PHP functions case sensitive?

Back 3

No.

Hint 3

Page 37

Front 4

What are the naming rules for a PHP function?

Back 4

Name must consist of only letters (a-z), numbers and the underscore character. It cannot start with a number.

Hint 4

Page 37

Front 5

What does the "return" keyword do in a fuction?

Back 5

Returns a value and exits the function immediately, The rest of the code in the function is ignored.

Hint 5

Page 38

Front 6

If the "return" keyword is not used in a function, is a value returned?

Back 6

Yes. If you do not return a value using the "return" keyword, then the function will return NULL when it completes. The concept of "void" functions does not really apply to PHP.

Hint 6

P 38

Front 7

Can you return a function by reference in PHP? If so, how?

Back 7

Yes. You can prepend the "&" to the function name to return function by reference. This is typically used to return a resource, such as a database connection, or implementing the Factory design pattern.

Example:

fuction &query($sql)
{
$result = mysql_query($sql);
return $result;
}

Caveats:
You must return a variable. If you return an expression or empty return statement.

Hint 7

P 39

Front 8

What are the three variable scopes in PHP?

Back 8

Global: available to all parts of the script
Function: available only inside the function
Class: available only inside a class

Hint 8

P 39 - 40

Front 9

How do you access global variables inside a function in PHP?

Back 9

There are two ways. First, you can use the "global" keyword.

Example:
$a = "Hello";
$b = "World";

function hello()
{
global $a, b$;
echo "$a $b";
}
hello(); //Displays "Hello World"

Second, use the $GLOBALS superglobal array.

Example:
$a = "Hello";
$b = "World";

function hello()
{
echo $GLOBALS['a'] . ' ' . $GLOBALS['b'];
}
hello(); //Displays "Hello World"

Hint 9

P 40 - 41

Front 10

How do you make arguments optional in a PHP function?

Back 10

To make arguments optional in PHP, you need to give them a default value in the function. Optional arguments must be right most in the list and take simple values, expressions are not allowed.

Example:
function hello($who = "World")
{
echo "Hello $who";
}
hello(); //display "Hello Word"
hello("Ted"); display "Hello Ted"

Hint 10

P 41

Front 11

What is a variable-length argument list in PHP?

Back 11

It is the ability to create a function that accepts a variable number of arguments.

Hint 11

P 42

Front 12

What are the three built-in functions in PHP to handle variable-length argument lists?

Back 12

func_num_args(): Return the total number of arguments passed into the function, declared or anonymous

func_get_arg(int): Return the argument at position int

func_get_args(): Return an array of all the arguments passed into the function

Hint 12

P 42 - 43

Front 13

How are arguments passed to a function by reference in PHP?

Back 13

Prefix the argument variable name with the by-reference operator "&".

Example:
$name = "Sam";
echo $name; //Output "Sam"
function setName(&$name)
{
$name = "Ted";
}
setName($name);
echo $name; //displays "Ted"

Hint 13

P43 - 44

Front 14

Can you pass an expression into a function by reference?

Back 14

No, only variables can be passed in by reference. If you attempt to pass in an expression by reference, you will get a fatal error.

Hint 14

P 44

Front 15

Can you create an optional parameter declared as by-reference in a function?

Back 15

Yes, but only in PHP 5 and above.

Example:
function setName(&$name = "Tim")
{
echo $name;
}

Hint 15

P 44