Copy this text file to a file named YourName_Midterm_Part1.txt. For example, JoeMcCullough_Midterm_Part1.txt. You will provide your answers to the problems in the "Answer:" sections indicated.
This portion of the test is to be completed without notes. Notes include
- previous assignments
- examples from in class
- anything from the internet
- etc
You are not allowed to execute php code in any form while taking this portion of the test. This includes
- from the browser
- from the command line
- from PHPStorm
After you have completed this portion of the midterm, attach the .txt file in an email to the following addresses:
Set the email subject as PHP Intermediate Midterm - Part 1
Notify a TA or the instructor when you have submitted Part 1. Part 2 will then be emailed to you.
!!!! WARNING !!!! - You will not be able to make revisions to your answers on Part 1 after you have started Part 2.
- Student name:
Define the following terms
a) variable
Definition:
b) constant
Definition:
c) operator
Definition:
d) operand
Definition:
e) statement
Definition:
f) expression
Definition:
g) syntax error
Definition:
h) relative path
Definition:
i) absolute path
Definition:
j) static website
Definition:
k) dynamic website:
Definition:
What is the role of the browser?
Answer:
What is the role of PHP?
Answer:
Briefly explain the processes that take place when a php file is requested from the browser.
Answer:
Define the following terms
a) cast
Definition:
b) dynamic typing
Definition:
List the basic (scalar) data types in PHP. Provide 2 example values for each type listed.
Answer:
When casting from a float to an int, what is the expected behavior?
Answer:
What is the basic data type that best represents each object/scenario?
a) contents of an email
Answer:
b) boxes of pizza
Answer:
c) number of donations a non-profit has received
Answer:
d) miles driven -
Answer:
e) is the account balance larger than the charge requested?
Answer:
f) number of students in a class
Answer:
g) is it raining outside?
Answer:
h) percent increase in stock value
Answer:
For each of the following expressions, list the value of the expression and the data type of the value.
a) 5 + 10
Answer:
b) (int) $x == $x
Answer:
c) 5.0 + 10
Answer:
d) "Number of siblings: " . $num_siblings
Answer:
e) 5 >= 2
Answer:
f) (int) 5.5 + 3.9
Answer:
f) (int) (5.5 + 3.9)
Answer:
g) "joe" == "JOE"
Answer:
Observe the following expression
<?php
$y = 10 + ($x = 5);
?>
a) What is the value of $x?
Answer:
b) What is the value of $y?
Answer:
c) Explain this behavior
Answer:
Come up with an example variable name and value for the following applications.
a). Whether it is raining outside or not
Answer:
b) The user's average typing words per minute is 56
Answer:
c) It's 98.6 degrees outside
Answer:
d) The user's social security number is 555442232
Answer:
Create 5 separate variables, with each individual variable representing a component of a date (for example, the day of the week). Provide example values for these variables.
Describe the general form of an if/else if/else statement
What will the following code print to the screen?
<?php
$x = 10;
$y = true;
if($x > 10){
if($x == 10 && $x % 2 == 0){
echo "$x is even and equal to 10";
}
}
else if($y){
echo '$y was true';
}
else if($x == 10){
echo '$x was 10';
}
else{
echo "Nothing happened";
}
?>
Output:
What will the following code print to the screen?
<?php
$x = 10;
$y = true;
if($x == 10 && $x % 2 == 0){
if($x > 10){
echo "$x is even and equal to 10";
}
}
else if($y){
echo '$y was true';
}
else if($x == 10){
echo '$x was 10';
}
?>
Output:
How are the following conditional statements different? What is the significance of this difference?
if($cond1){
// Do stuff if $cond1 is true
}
else if($cond2){
// Do stuff if $cond2 is true
}
vs
if($cond1){
// Do stuff if $cond1 is true
}
if($cond2){
// Do stuff if $cond2 is true
}
Answer:
Observe the following code:
<?php
$grade = 69;
if($grade >= 90){
echo "A";
}
else if($grade >= 80 && $grade < 90){
echo "B";
}
else if($grade >= 70 && $grade < 80){
echo "C";
}
else{
echo "F";
}
?>
Rewrite this code, removing the redundancies currently present but retaining the current behavior. Explain why you were able to eliminate the sections of code you did.
Answer:
Observe the following code:
<?php
$x = 15;
if($x > 10){
if($x % 2 == 1){
echo '$x is even and greater than 10';
}
}
?>
Rewrite this code, removing the nested if statements but retaining the same behavior.
Consider the following if statement:
<?php
if($current_balance >= $charge_amount || $overdraft_allowed){
// do something
}
else{
// do something else
}
?>
If the condition of the if-statement is false, what assumptions can we make within the else block regarding $current_balance, $charge_amount, and $overdraft_allowed?
Consider the following if statement:
<?php
if($temperature >= 80 && $condition == "sunny"){
// do something
}
else{
// do something else
}
?>
If the condition of the if-statement is false, what assumptions can we make within the else block regarding $temperature and $condition?
Look at the below code sample.
<?php
if ($language == "PHP") {
$what = "server-side scripting language";
}
else if ($language == "Javascript") {
$what = "client-side scripting language";
}
else if ($language == "English") {
$what = "human language";
}
else {
$what = "unknown value";
}
echo "$language is a $what.";
?>
...Given that code sample, what will be the output if the variable $language has the value:
a) "Javascript"
Answer:
b) "English"
Answer:
c) "Piglatin"
Answer:
Define the following terms:
a) element
Answer:
b) index
Answer:
A coworker of yours has written code of the following form:
<?php
$user_id_1 = 10;
$user_id_2 = 30;
$user_id_3 = 20;
$user_id_4 = 90;
$user_id_5 = 70;
send_welcome_email($user_id_1);
send_welcome_email($user_id_2);
send_welcome_email($user_id_3);
send_welcome_email($user_id_4);
send_welcome_email($user_id_5);
?>
What arguments would you use to convince the coworker to implement a $user_ids array instead of using individual $user_id_ variables?
Answer:
Assume the array $animals is non-empty. The following questions should be answered for the array in general terms. You do not need to see the contents of the array in order to answer the questions.
a) Assign the number of elements in $animals to the variable $x.
Answer:
b) What is the last index of $animals?
Answer:
c) What is the value of the last element of $animals?
Answer:
Consider the following array
$x = [2,0,1,4,3];
What are the values of the following expressions?
a) 2 * $x[0]
Answer:
b) $x[0] * $x[0]
Answer:
c) $x[count($x)-1]
Answer:
d) $x[count($x)-2] + $x[count($x) - count($x)]
Answer:
e) $x[$x[0]]
Answer:
Define the following terms
a) key
Answer:
b) key-value pair
Answer:
For the following array, write code that could be used to retrieve the requested values within the array:
$patients = array(
array(
'name' => 'Kurt Vonnegut',
'illness' => 'Sore Throat',
'admittance_time' => '04:30 PM'
),
array(
'name' => 'Noam Chomsky',
'illness' => 'Twisted Ankle',
'admittance_time' => '01:30 AM'
),
array(
'name' => 'Hacker McHackerson',
'illness' => 'Carpel Tunnel',
'admittance_time' => '10:30 PM'
)
)
a) 'Sore Throat'
Answer:
b) '01:30 AM':
Answer:
c) 'Hacker McHackerson':
Answer:
Precisely define the structure of a for loop.
Answer:
Precisely define the structure of a while loop.
Answer:
a) In general, when would a while loop be preferred over a for loop?
Answer:
b) Provide an example scenario where using a while loop may be preferred over a using for loop
Answer:
Precisely define the structure of a foreach loop.
Answer:
Why is it generally preferred to use a foreach loop to iterate over an array?
Answer:
Observe the following array definition:
$nums = [5,3,9,12,6];
Create a foreach loop that would print out each element of $nums on its own line in the browser.
Answer:
The built in php function mysql_fetch_assoc will fetch a row from a query
result and return the row as an associative array. If no more rows are available
to be fetched from the query result, the mysql_fetch_assoc function returns
boolean FALSE.
Observe the following PHP code, which demonstrates a common idiom for iterating through a query result.
<?php
// Make a MySQL Connection
$query = "SELECT * FROM example";
$result = mysql_query($query) or die(mysql_error());
while($row = mysql_fetch_assoc($result)){
echo $row['name']. " - ". $row['age'];
echo "<br />";
}
?>
Explain precisely how the loop header while($row = mysql_fetch_assoc($result))
allows us to iterate over each result from the query. How can the return value
of mysql_fetch_assoc stop the loop if it's being assigned to $row?
Answer:
Explain the difference between a function definition and a function call
Answer:
What is the primary purpose of a return statement in a function? Beyond its primary purpose, what is an additional consequence of using a return statement in a function?
Answer:
What will the following program print?
<?php
function say_a(){
echo "A";
}
function say_b(){
say_a();
echo "B";
}
function say_c(){
say_a();
say_b();
echo "C";
}
say_c();
say_c();
?>
Answer:
What will the following program print?
<?php
function overwrite($x, $y){
$x = 10;
return $x + $y;
}
$x = 5;
$y = 10;
echo overwrite($x, $y);
echo "x: $x<br>";
echo "y: $y<br>";
?>
Answer:
Observe the following true PHP expressions:
- 1 % 2 == 1
- 2 % 2 == 0
- 3 % 2 == 1
- 4 % 2 == 0
- 5 % 2 == 1
- 6 % 2 == 0
- 7 % 2 == 1
- 8 % 2 == 0
With these expressions in mind, create a function called is_even that meets the following conditions:
- The function takes a single argument, which will be an integer
- The function should return true if that integer is even
- The function should return false if that integer is odd
Answer:
Define the following terms
a) constructor
Definition:
b) object
Definition:
c) property
Definition:
d) method
Definition:
e) member
Definition:
a) Explain the difference between an instance method and a static method
Answer:
b) Provide an example use case for a static method
Answer:
c) Provide an example use case for an instance method
Answer:
Provide an example scenario demonstrating the usefulness of a setter method (as opposed to directly assigning a value to a property via $obj->property = val)
Answer:
Explain what $this represents in an instance method definition.
Answer: