String type (single vs double quotes) in PHP - Practice Questions

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of variable interpolation in strings

What is the output of the following PHP code?

PHP

<?php
$name = "Alice";
echo 'Hello, $name!';
?>

A Hello, Alice!

B Syntax error

C Hello, !

D Hello, $name!

💡 Hint

Remember how single quotes treat variables inside strings in PHP.

In PHP, single-quoted strings do not parse variables. So '$name' is treated as literal text.

❓ Predict Output

intermediate

Escape sequences in single vs double quotes

What will this PHP code output?

PHP

<?php
echo "Line1\nLine2";
echo '\nLine3';
?>

A

Line1
Line2\nLine3

B Line1\nLine2\nLine3

C

Line1
Line2
Line3

D

Line1\nLine2
Line3

💡 Hint

Check how escape sequences like \n behave in single and double quotes.

In double quotes, \n is interpreted as a newline character, so "Line1\nLine2" outputs two lines. In single quotes, escape sequences like \n are not interpreted, so '\nLine3' outputs a literal backslash and 'n' followed by 'Line3'. The combined output is: Line1 Line2\nLine3

🔧 Debug

advanced

Why does this string concatenation fail?

Consider this PHP code snippet. Why does it cause an error?

PHP

<?php
$name = "Bob";
echo 'Hello, ' . $name . '!';
echo 'He said, "Hi!"';
echo 'It\'s sunny';
?>

A No error; all lines run fine.

B The third echo causes a syntax error because the single quote inside is not escaped properly.

C The first echo causes a syntax error because concatenation uses wrong operator.

D The second echo causes a syntax error because double quotes inside single quotes are not allowed.

💡 Hint

Look carefully at how quotes inside strings are escaped.

There is no syntax error. Concatenation with '.' is correct. Double quotes inside single-quoted strings are literal and need no escaping. The third echo 'It\'s sunny' correctly escapes the single quote with a backslash, so it runs fine outputting: It's sunny.

❓ Predict Output

advanced

Output of complex variable interpolation

What is the output of this PHP code?

PHP

<?php
$fruit = "apple";
echo "I have an {$fruit}s.";
?>

A I have an apple s.

B I have an apples.

C I have an {$fruit}s.

D I have an apple.

💡 Hint

Look at how curly braces help with variable interpolation.

Curly braces tell PHP where the variable name ends, so {$fruit}s becomes 'apple' + 's'.

🧠 Conceptual

expert

Difference in performance between single and double quotes

Which statement about single and double quoted strings in PHP is TRUE?

A Double quoted strings are faster because they allow variable interpolation.

B There is no performance difference between single and double quoted strings in PHP.

C Single quoted strings are always faster because PHP does not parse variables or escape sequences inside them.

D Single quoted strings cause syntax errors if they contain variables.

💡 Hint

Think about what PHP does internally when parsing strings.

Single quoted strings are faster because PHP treats them as literal text without parsing variables or most escape sequences (except \' and \\).