Chapter 4 - Expressions and Control Flow in PHP

Question 1

What is an expression?

Answer 1

A combination of values, variables, operators and functions that results in a value.

Question 2

What is a unary operator?

Answer 2

Takes a single operand.

Eg. $a++ or -$a

Question 3

What is a binary operator?

Answer 3

Represents the bulk of php operators, including addition, subtraction, multiplication and division.

Question 4

What is a binary operator?

Answer 4

Represents the bulk of php operators, including addition, subtraction, multiplication and division.

Question 5

What is a literal?

Answer 5

The simplest form of an expression, which simply means something that evaluates itself, such as the number 15 or the string “Hello”.

Question 6

What is a ternary operator?

Answer 6

Takes the form ? x: y. It’s a terse, single-line if statement that chooses between two expressions, depending on the result of a third one.

Question 7

What is the associativity of

Answer 7

None

Question 8

What is the associativity of (string) - cast to a string?

Answer 8

Right

Question 9

What is the associativity of % Modulus?

Answer 9

Left

Question 10

What does a relational operator do?

Answer 10

Tests two operands and returns a Boolean result of either True or False.

Question 11

what are the three types of relational operators?

Answer 11

Equality
Comparison
Logical

Question 12

What is a conditional?

Answer 12

Conditionals alter program flow. They enable you to ask questions about certain things and respond to the answers you get in different ways.

Question 13

Give an example of PHP code for an if - else statement:

Question 14

What does the SWITCH statement do?

Answer 14

It is useful in cases in which one variable or the result of an expression can have multiple values, which should each trigger a different function.

Question 15

What does the ? Operator do?

Answer 15

It passes an expression that it must evalulate, along with two statements to execute. One for when the expression evaluates to TRUE and the other for when it is FALSE.

Question 16

What is the difference between implicit and explicit casting?

Answer 16

PHP allows you to declare a var and its type simply by using it. It also automatically converts values from one type to another whenever required. This is called IMPLICIT CASTING.

Sometimes this might not be what you want. What if you want something else, you can cast the type to be a specific int instead of double. This is EXPLICIT CASTING.

Question 17

What does the ? Operator do?

Answer 17

It passes an expression that it must evaluate, along with two statements to execute. One for when the expression evaluates to TRUE and the other for when it is FALSE.

Question 18

What is the difference between implicit and explicit casting?

Answer 18

PHP allows you to declare a var and its type simply by using it. It also automatically converts values from one type to another whenever required. This is called IMPLICIT CASTING.

Sometimes this might not be what you want. What if you want something else, you can cast the type to be a specific int instead of double. This is EXPLICIT CASTING.

Question 19

What is PHP Dynamic Linking?

Answer 19

Splitting a website into different components makes for a much more useable code.

Question 20

What actual underlying values are represented by TRUE and FALSE?

Answer 20

In PHP, TRUE represents the value 1 and FALSE represents NULL, which can be thought of as “nothing” and is output as an empty string.

Question 21

What are the simplest two forms of expression?

Answer 21

Literals such as numbers and strings

Variables, which simply evaluate themselves.

Question 22

What is the difference between unary, binary and ternary operators?

Answer 22

The difference between unary, binary and ternary operators is the number of operands each requires - one, two and three, respectively.

Question 23

What is the best way to force your own operator precedence?

Answer 23

The best way to force your own operator precedence is to place parantheses around subexpressions to which you wish to give high precedence.

Question 24

What is meant by operator associativity?

Answer 24

Operator associativity refers to the direction of processing (left to right or right to left).

Question 25

When would you use the == identity operator?

Answer 25

You use the identity operator when you wish to bypass PHP’s automatic operand type changing (also called type casting).

Question 26

Name the three conditional statement types:

Answer 26

The three conditional statement types are if, switch, and the ?: operator

Question 27

What command can you use to skip the current iteration of a loop and move on to the next one?

Answer 27

To skip the current iteration of a loop and move on to the next one, use a continue statement.

Question 28

Why is a for loop more powerful than a while loop?

Answer 28

Loops using for statements are more powerful than while loops, because they support two additional parameters to control the loop handling.

Question 29

How do if and while statements interpret conditional expressions of different data types?

Answer 29

Most conditional expressions in if and while statements are literal (or Boolean) and therefore trigger execution when they evaluate to TRUE. Numeric expressions trigger execution when they evaluate to a nonzero value. String expressions trigger execution when they evaluate to a nonempty string. A NULL value is evaluated as false and therefore does not trigger execution.