String interpolation in double quotes in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of simple variable interpolation

What is the output of this PHP code?

PHP

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

A Hello, $name!

B Hello, Alice!

C Hello, !

D Hello, name!

💡 Hint

Variables inside double quotes are replaced by their values.

In PHP, variables inside double quotes are replaced by their values. So $name becomes Alice.

❓ Predict Output

intermediate

Output with array element interpolation

What will this PHP code output?

PHP

<?php
$colors = ['red', 'green', 'blue'];
echo "My favorite color is $colors[1].";
?>

A My favorite color is Array[1].

B My favorite color is green.

C My favorite color is .

D My favorite color is $colors[1].

💡 Hint

Array elements inside double quotes need special syntax.

PHP does not parse $colors[1] inside double quotes directly. It interpolates $colors to "Array" and treats [1]. as literal text.

❓ Predict Output

advanced

Correct syntax for array element interpolation

Which option outputs: My favorite color is green. ?

PHP

<?php
$colors = ['red', 'green', 'blue'];
// Fill in the echo statement
?>

A echo "My favorite color is $colors{1}.";

B echo "My favorite color is ${colors[1]}.";

C echo "My favorite color is {$colors[1]}.";

D echo "My favorite color is $colors[1].";

💡 Hint

Use curly braces to clearly specify the array element inside double quotes.

Using {$colors[1]} inside double quotes tells PHP to replace it with the array element at index 1.

❓ Predict Output

advanced

Output with object property interpolation

What is the output of this PHP code?

PHP

<?php
class Person {
  public $name = 'Bob';
}
$p = new Person();
echo "Hello, $p->name!";
?>

A Hello, $p->name!

B Hello, !

C Hello, Object->name!

D Hello, Bob!

💡 Hint

Object properties like $p->name can be interpolated directly inside double quotes.

In PHP, object properties like $p->name are parsed and replaced by their values inside double quotes.

❓ Predict Output

expert

Correct interpolation of object property

Which option outputs: Hello, Bob! ?

PHP

<?php
class Person {
  public $name = 'Bob';
}
$p = new Person();
// Fill in the echo statement
?>

A echo "Hello, {$p->name}!";

B echo "Hello, $p->name!";

C echo "Hello, ${p->name}!";

D echo "Hello, $p->{name}!";

💡 Hint

Use curly braces around the entire object property expression.

Using {$p->name} inside double quotes tells PHP to replace it with the object's property value.