Escape sequences in strings in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an escape sequence in PHP strings?

An escape sequence is a way to include special characters in a string that would otherwise be hard to type or have special meaning, like new lines or quotes. It starts with a backslash (\).

beginner

How do you write a newline character inside a PHP string?

Use the escape sequence \n inside double-quoted strings to add a new line.

beginner

What escape sequence do you use to include a double quote inside a double-quoted PHP string?

Use \" to include a double quote inside a double-quoted string.

intermediate

What happens if you use single quotes in PHP strings regarding escape sequences?

In single-quoted strings, only \\' and \\ are recognized as escape sequences. Others like \n are treated as normal characters.

beginner

List three common escape sequences in PHP strings and their meanings.

\n = new line, \t = tab, \" = double quote inside double-quoted string.

Which escape sequence adds a tab space in a PHP double-quoted string?

A \t

B \n

C \r

D \b

The escape sequence \t adds a tab space inside double-quoted strings.

How do you write a backslash character inside a PHP string?

A \\

B \n

C \"

D \t

Use \\ to represent a single backslash character in a string.

In PHP, which escape sequences work inside single-quoted strings?

A None

B \\ and \' only

C All escape sequences

D \n and \t

Only \\ and \' are recognized as escape sequences inside single-quoted strings.

What will this PHP code output? echo "Hello\nWorld";

A Hello\nWorld

B Error

C Hello World

D Hello (new line) World

The \n creates a new line, so Hello and World appear on separate lines.

Which escape sequence inserts a carriage return in PHP strings?

A \t

B \n

C \r

D \b

The escape sequence \r inserts a carriage return character.

Explain how escape sequences work in PHP strings and give examples.

Think about how to include special characters inside strings.

Describe the difference between escape sequences in single-quoted and double-quoted PHP strings.

Consider which escape sequences are processed in each string type.

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