Escape sequences in strings in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of escape sequences in double-quoted strings

What is the output of the following PHP code?

PHP

<?php
echo "Line1\nLine2\tTabbed";
?>

A Line1\nLine2\tTabbed

B Line1 Line2 Tabbed

C

Line1
Line2	Tabbed

D Line1\nLine2 Tabbed

💡 Hint

Remember that double-quoted strings interpret escape sequences like \n and \t.

In PHP, double-quoted strings interpret escape sequences. \n creates a new line, and \t adds a tab space. So the output shows Line1, then a new line, then Line2 followed by a tab and 'Tabbed'.

❓ Predict Output

intermediate

Escape sequences in single-quoted strings

What will this PHP code output?

PHP

<?php
echo 'Line1\nLine2\tTabbed';
?>

A

Line1
Line2	Tabbed

B Line1\nLine2\tTabbed

C Line1 Line2 Tabbed

D Line1\nLine2 Tabbed

💡 Hint

Single-quoted strings do not interpret most escape sequences except \' and \\.

In PHP, single-quoted strings treat most escape sequences as literal characters. So \n and \t are printed as two characters \ and n or t, not as newline or tab.

❓ Predict Output

advanced

Using variable interpolation with escape sequences

What is the output of this PHP code?

PHP

<?php
$name = "Anna";
echo "Hello, $name\nWelcome!";
?>

A

Hello, $name
Welcome!

B Hello, $name\nWelcome!

C Hello, Anna\nWelcome!

D

Hello, Anna
Welcome!

💡 Hint

Double-quoted strings allow variable interpolation and escape sequences.

In double-quoted strings, PHP replaces $name with its value 'Anna' and interprets \n as a newline. So the output is Hello, Anna followed by a new line and Welcome!

❓ Predict Output

advanced

Escape sequences with curly braces in variable interpolation

What does this PHP code output?

PHP

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

A I have an apples.

B I have an apple s.

C I have an {$fruit}s.

D I have an $fruits.

💡 Hint

Curly braces help PHP know where the variable name ends in strings.

Using {$fruit}s tells PHP to replace $fruit with 'apple' and then add 's' after it, resulting in 'apples'.

🧠 Conceptual

expert

Understanding complex escape sequences in strings

Which option correctly describes the output of this PHP code snippet?

PHP

<?php
echo "Path: C:\\Users\\John\nNew Line";
?>

A

Path: C:\Users\John
New Line

B Path: C:\\Users\\John\nNew Line

C

Path: C:UsersJohn
New Line

D Path: C:\Users\John\nNew Line

💡 Hint

Remember that \\ in double quotes prints a single backslash, and \n prints a newline.

In PHP, double-quoted strings interpret \\ as a single literal backslash. So C:\\Users\\John becomes C:\Users\John, and \n becomes a newline. The output is two lines: 'Path: C:\Users\John' and 'New Line'.

Practice

1. Which escape sequence in PHP represents a new line inside a double-quoted string?

easy

A. \\

B. \t

C. \r

D. \n

Solution

1. Step 1: Understand common escape sequences

   In PHP, \n is used to represent a new line character inside double-quoted strings.

2. Step 2: Identify the correct escape sequence for new line

   Among the options, \n is the standard escape sequence for a new line.

3. Final Answer:

   \n -> Option D

4. Quick Check:

   New line escape sequence = \n [OK]

Hint: New line is always \n inside double quotes [OK]

Common Mistakes:

• Confusing \n with \t (tab)
• Using single quotes which don't parse escapes
• Thinking \r is new line

2. Which of the following is the correct way to include a double quote inside a double-quoted string in PHP?

easy

A. This is a "quote" inside

B. This is a ""quote"" inside

C. This is a \"quote\" inside

D. This is a 'quote' inside

Solution

1. Step 1: Recognize string delimiters and escaping rules

   In PHP, to include a double quote inside a double-quoted string, you must escape it with a backslash (\").

2. Step 2: Check each option for correct syntax

   "This is a \"quote\" inside" correctly escapes the double quotes. Unescaped double quotes like in "This is a "quote" inside" cause syntax errors. Adjacent string literals like "This is a ""quote"" inside" cause syntax errors. "This is a 'quote' inside" uses single quotes and does not include double quotes.

3. Final Answer:

   This is a \"quote\" inside -> Option C

4. Quick Check:

   Escape double quotes inside double quotes with \" [OK]

Hint: Escape double quotes inside "..." with \" [OK]

Common Mistakes:

• Not escaping double quotes inside double quotes
• Using single quotes but escaping double quotes
• Unescaped quotes causing syntax errors

3. What will be the output of the following PHP code?

$str = "Hello\tWorld\n";
echo $str;

medium

A. Hello World
(with tab and new line interpreted)

B. Hello World\n

C. Hello World\n

D. Hello\tWorld\n

Solution

1. Step 1: Understand escape sequences in double-quoted strings

   In PHP, \t is a tab character and \n is a new line character. Both are interpreted inside double quotes.

2. Step 2: Predict the output of echo $str

   The string will print "Hello", then a tab space, then "World", then a new line. So the output shows a tab space and a line break.

3. Final Answer:

   Hello World (with tab and new line interpreted) -> Option A

4. Quick Check:

   \t and \n produce tab and new line in output [OK]

Hint: Escape sequences in double quotes print special chars [OK]

Common Mistakes:

• Thinking \t prints literally as \t
• Ignoring new line effect
• Using single quotes which don't parse escapes

4. Identify the error in this PHP code snippet:

echo "Path to file: C:\newfolder\file.txt";

medium

A. Double quotes inside string are not escaped

B. Backslashes are not escaped, causing incorrect output

C. Single quotes should be used instead of double quotes

D. No error, code runs correctly

Solution

1. Step 1: Analyze backslash usage in double-quoted strings

   In PHP, backslash (\) is an escape character. To print a literal backslash, you must escape it as \\.

2. Step 2: Check the given string for backslash escaping

   The string uses single backslashes before 'n' and 'f', which PHP interprets as escape sequences (\n = newline, \f = form feed). This changes the output unexpectedly.

3. Final Answer:

   Backslashes are not escaped, causing incorrect output -> Option B

4. Quick Check:

   Escape backslash as \\ to print it literally [OK]

Hint: Escape backslash as \\ inside double quotes [OK]

Common Mistakes:

• Not escaping backslashes
• Confusing escape sequences with literal backslash
• Using single quotes but expecting escapes

5. You want to create a PHP string that outputs exactly: She said, "Hello\World!" including the quotes and backslash. Which code snippet achieves this?

hard

A. echo "She said, \"Hello\\World!\"";

B. echo 'She said, "Hello\World!"';

C. echo "She said, "Hello\World!"";

D. echo "She said, \"HelloWorld!\"";

Solution

1. Step 1: Identify characters needing escaping

   The string includes double quotes and a backslash. Inside double-quoted PHP strings, double quotes and backslashes must be escaped with a backslash.

2. Step 2: Check each option for correct escaping

   echo "She said, \"Hello\\World!\""; escapes double quotes as \" and backslash as \\, correctly producing the desired output. echo 'She said, "Hello\World!"'; uses single quotes but escapes double quotes unnecessarily and backslash is not escaped properly. echo "She said, "Hello\World!""; has unescaped double quotes causing syntax error. echo "She said, \"HelloWorld!\""; escapes double quotes but not the backslash before 'World', so backslash is interpreted as escape sequence.

3. Final Answer:

   echo "She said, \"Hello\\World!\""; -> Option A

4. Quick Check:

   Escape " as \" and \ as \\ inside "..." [OK]

Hint: Escape " as \" and \ as \\ inside double quotes [OK]

Common Mistakes:

• Not escaping backslash
• Unescaped double quotes causing errors
• Using single quotes but expecting escapes