Escape sequences in strings in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print a new line using an escape sequence.

PHP

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

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

A\n

B\t

C\r

D\\

Attempts:

3 left

💡 Hint

Common Mistakes

Using \t which adds a tab space instead of a new line.

Using \\ which prints a backslash.

The escape sequence \n creates a new line in the output.

2fill in blank

medium

Complete the code to include a tab space between words.

PHP

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

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

A\t

B\n

C\r

D\\

Attempts:

3 left

💡 Hint

Common Mistakes

Using \n which adds a new line instead of a tab.

Using \\ which prints a backslash.

The escape sequence \t adds a horizontal tab space between words.

3fill in blank

hard

Fix the error in the code to correctly print a backslash character.

PHP

<?php
echo "This is a backslash: [1]";
?>

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

A\t

B\\

C\n

D\

Attempts:

3 left

💡 Hint

Common Mistakes

Using a single backslash which causes an error or unexpected output.

Using \n or \t which print new line or tab instead.

To print a single backslash, you need to escape it with another backslash: \\.

4fill in blank

hard

Fill both blanks to print a double quote inside a string.

PHP

<?php
echo "She said: [1]Hello[2]";
?>

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

A\"

B\n

C"

D\t

Attempts:

3 left

💡 Hint

Common Mistakes

Using unescaped double quotes which break the string.

Using single quotes which do not work inside double-quoted strings.

To print double quotes inside a double-quoted string, use the escape sequence \".

5fill in blank

hard

Fill all three blanks to print a path with backslashes and a new line.

PHP

<?php
echo "C:[1]Users[2]Documents[3]";
?>

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

A\\

B\n

C/

D\t

Attempts:

3 left

💡 Hint

Common Mistakes

Using single backslashes which cause errors.

Using forward slashes instead of backslashes.

Forgetting to add a new line escape sequence.

Backslashes in paths must be escaped as \\. To add a new line, use \n.

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