Data Types in PHP

  $age = 25; // Integer
echo $age; 

  Output:

25

$price = 19.99;
echo $price;

19.99

$price = 19.99;
echo $price;

19.99

$isStudent = true; // Boolean
echo $isStudent; 

Output:

1 (true is displayed as 1)

Compound Types 

Compound types can hold multiple values. There are 2 compound types in PHP:

5) Array

Stores multiple values in a single variable.

Example:

$fruits = ["apple", "banana", "cherry"]; // Array
print_r($fruits); 

Array
(
    [0] => apple
    [1] => banana
    [2] => cherry
)

 6) Object

Stores instances of classes (used in object-oriented programming).

Example:

$fruits = ["apple", "banana", "cherry"]; // Array
print_r($fruits); 

Array
(
    [0] => apple
    [1] => banana
    [2] => cherry
)

Special Types 

Special types are unique and don’t fall into scalar or compound categories.

There are 2 special types in PHP:

7) NULL

Represents a variable with no value.

Example:

$address = null; // NULL
echo $address;

(nothing, because null means no value)

8) Resource

Stores a reference to an external resource (like a database connection or file handle).

Example:

$file = fopen("example.txt", "r"); // Resource
echo gettype($file); 

Resource

15+ interview questions on PHP data types with answers and examples

Question 1. What are the data types in PHP?

Answer: PHP supports 8 basic data types, divided into three categories:

• Scalar Types: Integer, Float, String, Boolean.
• Compound Types: Array, Object.
• Special Types: NULL, Resource.

Question 2. What is an integer in PHP?

Answer: An integer is a scalar data type that stores whole numbers (positive or negative).

Example:

$age = 25; // Integer
echo $age; 

Output:

25

Question 3. What is a float in PHP?

Answer: A float (or double) is a scalar data type that stores decimal numbers.

Example:

$price = 19.99; // Float
echo $price; 

Output:

19.99

Question 4. What is a string in PHP?

Answer: A string is a scalar data type that stores text (a sequence of characters).

Example:

$name = "John"; // String
echo $name; 

Output:

John

Question 5. What is a boolean in PHP?

Answer: A boolean is a scalar data type that stores true or false.

Example:

$isStudent = true; // Boolean
echo $isStudent; 

Output:

1 (true is displayed as 1)

Question 6. What is an array in PHP?

Answer: An array is a compound data type that stores multiple values in a single variable.

Example:

$fruits = ["apple", "banana", "cherry"]; // Array
print_r($fruits);

Output:

Array ( [0] => apple [1] => banana [2] => cherry )

Question 7. What is an object in PHP?

Answer: An object is a compound data type that stores an instance of a class (used in object-oriented programming).

Example:

class Car {
    public $color = "red";
}
$myCar = new Car(); // Object
echo $myCar->color; 

Output:

red

Question 8. What is NULL in PHP?

Answer: NULL is a special data type that represents a variable with no value.

Example:

$address = null; // NULL
echo $address; 

Output:

(nothing, because null means no value)

Question 9. What is a resource in PHP?

Answer: A resource is a special data type that stores a reference to an external resource (like a database connection or file handle).

Example:

$file = fopen("example.txt", "r"); // Resource
echo gettype($file); 

Output:

resource

Question 10. How do you check the data type of a variable in PHP?

Answer: Use the gettype() function to check the data type of a variable.

Example:

$age = 25;
echo gettype($age); 

Output:

integer

Question 11. How do you convert a string to an integer in PHP?

Answer: Use the (int) or intval() function to convert a string to an integer.

Example:

$number = "10";
$intNumber = (int)$number; // Convert to integer
echo $intNumber; 

Output:

10

Question 12. How do you convert an integer to a string in PHP?

Answer: Use the (string) or strval() function to convert an integer to a string.

Example:

$age = 25;
$strAge = (string)$age; // Convert to string
echo $strAge; 

Output:

25

Question 13. What is type juggling in PHP?

Answer: Type juggling is the automatic conversion of one data type to another by PHP, depending on the context.

Example:

$number = "10"; // String
$sum = $number + 5; // PHP converts "10" to integer
echo $sum; 

Output:

15

Question 14. What is type casting in PHP?

Answer: Type casting is the manual conversion of one data type to another using syntax like (int), (string), etc.

Example:

$price = "19.99"; // String
$floatPrice = (float)$price; // Convert to float
echo $floatPrice; 

Output:

19.99