String concatenation operator in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to concatenate two strings using the correct operator.

PHP

<?php
$greeting = "Hello" [1] " World!";
echo $greeting;
?>

Drag options to blanks, or click blank then click option'

A+

B&&

C&

D.

Attempts:

3 left

💡 Hint

Common Mistakes

Using + instead of . for string concatenation.

Using && which is a logical operator.

In PHP, the dot . operator is used to join (concatenate) strings.

2fill in blank

medium

Complete the code to join the variables $first and $last into $fullName.

PHP

<?php
$first = "John";
$last = "Doe";
$fullName = $first [1] $last;
echo $fullName;
?>

Drag options to blanks, or click blank then click option'

A,

B+

C.

D&&

Attempts:

3 left

💡 Hint

Common Mistakes

Using + which causes errors with strings.

Using commas which do not concatenate strings.

The dot . operator joins two strings stored in variables.

3fill in blank

hard

Fix the error in concatenating $a and $b with a space between them.

PHP

<?php
$a = "Good";
$b = "Morning";
$result = $a [1] " " [2] $b;
echo $result;
?>

Drag options to blanks, or click blank then click option'

A.

B+

C,

D&&

Attempts:

3 left

💡 Hint

Common Mistakes

Using + which causes errors.

Using commas which do not concatenate strings.

Use the dot . operator to concatenate multiple strings and variables.

4fill in blank

hard

Fill both blanks to concatenate $city and $country with a comma and space between.

PHP

<?php
$city = "Paris";
$country = "France";
$location = $city[1] ", " [2] $country;
echo $location;
?>

Drag options to blanks, or click blank then click option'

A.

B+

C,

D&&

Attempts:

3 left

💡 Hint

Common Mistakes

Using + which is for numbers.

Using commas which do not concatenate strings.

Use the dot . operator to join strings and literals.

5fill in blank

hard

Fill all three blanks to build a greeting with $name and $day.

PHP

<?php
$name = "Alice";
$day = "Monday";
$message = "Hello, "[1] $name [2] "! Today is " [3] $day;
echo $message;
?>

Drag options to blanks, or click blank then click option'

A+

B.

C,

D&&

Attempts:

3 left

💡 Hint

Common Mistakes

Using + which causes errors with strings.

Using commas or && which do not concatenate strings.

Use the dot . operator to join all parts of the greeting string.

Practice

1. What does the dot (.) operator do in PHP?

easy

A. Joins two strings together

B. Adds two numbers

C. Compares two strings

D. Divides two numbers

Solution

1. Step 1: Understand the dot operator usage

   In PHP, the dot operator is used to join or concatenate strings.

2. Step 2: Differentiate from other operators

   It does not perform arithmetic or comparison; it only combines strings.

3. Final Answer:

   Joins two strings together -> Option A

4. Quick Check:

   Dot operator = string join [OK]

Hint: Dot (.) always joins strings in PHP [OK]

Common Mistakes:

• Confusing dot with plus (+) for addition
• Thinking dot compares strings
• Using dot for division

2. Which of the following is the correct way to concatenate two strings $a and $b in PHP?

easy

A. $a + $b

B. $a . $b

C. $a & $b

D. $a * $b

Solution

1. Step 1: Identify the concatenation operator

   PHP uses the dot (.) operator to join strings, so $a . $b is correct.

2. Step 2: Check other operators

   Plus (+) adds numbers, ampersand (&) is bitwise AND, and asterisk (*) is multiplication.

3. Final Answer:

   $a . $b -> Option B

4. Quick Check:

   Dot (.) concatenates strings [OK]

Hint: Use dot (.) to join strings, not plus (+) [OK]

Common Mistakes:

• Using + instead of . for strings
• Using & or * operators mistakenly
• Missing the dot operator

3. What is the output of the following PHP code?

$greeting = "Hello";
$name = "Alice";
echo $greeting . ", " . $name . "!";

medium

A. Hello,Alice!

B. Hello Alice!

C. Hello, Alice!

D. Hello . , . Alice . !

Solution

1. Step 1: Analyze string concatenation

   The code joins "Hello", ", ", "Alice", and "!" using the dot operator.

2. Step 2: Combine strings step-by-step

   "Hello" . ", " = "Hello, " and then "Hello, " . "Alice" = "Hello, Alice" and finally "Hello, Alice" . "!" = "Hello, Alice!"

3. Final Answer:

   Hello, Alice! -> Option C

4. Quick Check:

   Concatenate with dot = Hello, Alice! [OK]

Hint: Dot joins strings exactly as written [OK]

Common Mistakes:

• Missing spaces inside strings
• Expecting plus (+) to work
• Confusing output with literal dots

4. Find the error in this PHP code:

$first = "Good";
$second = "Morning";
echo $first + " " + $second;

medium

A. Using double quotes incorrectly

B. Missing semicolon after echo

C. Variables not declared

D. Using + instead of . for string concatenation

Solution

1. Step 1: Identify operator misuse

   The code uses + to join strings, but PHP requires the dot (.) operator for concatenation.

2. Step 2: Confirm other syntax is correct

   Semicolons are present, variables declared, and quotes are correct.

3. Final Answer:

   Using + instead of . for string concatenation -> Option D

4. Quick Check:

   Use dot (.) not plus (+) for strings [OK]

Hint: Remember: + is for numbers, . is for strings [OK]

Common Mistakes:

• Using + to join strings
• Thinking + works like in JavaScript
• Ignoring PHP string rules

5. You want to create a full name string from $firstName and $lastName with a space between them. Which code correctly does this in PHP?

hard

A. $fullName = $firstName . " " . $lastName;

B. $fullName = $firstName + " " + $lastName;

C. $fullName = $firstName . $lastName;

D. $fullName = '$firstName $lastName';

Solution

1. Step 1: Understand string concatenation with space

   To join first and last names with a space, you must add " " explicitly between them using dot operators.

2. Step 2: Evaluate each option

   A misses the space, B uses + which is invalid for strings, D uses single quotes so variables are not interpolated.

3. Final Answer:

   $fullName = $firstName . " " . $lastName; -> Option A

4. Quick Check:

   Dot with space string joins names correctly [OK]

Hint: Add space as " " between strings with dot [OK]

Common Mistakes:

• Forgetting space between names
• Using + instead of .
• Assuming variables parse inside single quotes