String interpolation in double quotes in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is string interpolation in PHP when using double quotes?

String interpolation means PHP replaces variables inside double-quoted strings with their values automatically.

beginner

How do you include a variable inside a double-quoted string in PHP?

Simply write the variable name inside the double quotes, like "$name". PHP will replace it with the variable's value.

beginner

What happens if you use single quotes instead of double quotes for strings with variables in PHP?

Variables inside single quotes are treated as plain text, so no interpolation happens.

intermediate

How can you include an array element inside a double-quoted string in PHP?

Use curly braces around the variable and key, like "{$array['key']}" to interpolate the value.

intermediate

Why might you use curly braces {} around variables in double-quoted strings?

Curly braces help PHP understand where the variable name ends, especially when followed by letters or numbers.

What will this PHP code output? <br>

$name = "Anna"; echo "Hello, $name!";

A Error

B Hello, $name!

C Hello, !

D Hello, Anna!

PHP replaces $name with its value inside double quotes.

Which string syntax allows variable interpolation in PHP?

A Double quotes (" ")

B Single quotes (' ')

C Backticks (` `)

D None of the above

Only double quotes allow variables to be replaced with their values.

How do you correctly interpolate an array element $arr['key'] inside a double-quoted string?

A "{$arr['key']}"

B "$arr['key']"

C '$arr[key]'

D "$arr[key]"

Curly braces are needed to correctly parse array elements inside strings.

What will this output? <br>

$var = "day"; echo "Today is $var1";

A Today is day1

B Today is day

C Today is

D Today is $var1

PHP tries to interpolate $var1, which is undefined, treating it as an empty string (with a notice), so the output is "Today is ".

Why use curly braces in "Hello, {$name}123"?

A To add numbers to the string

B To separate variable name from following text

C To comment inside string

D To make string uppercase

Curly braces tell PHP where the variable name ends.

Explain how string interpolation works in PHP double-quoted strings.

Think about how PHP reads variables inside strings.

Describe how to include an array element inside a double-quoted string in PHP.

Remember how PHP parses complex variables inside strings.