Definition and Usage

PHP Version
4+

The is_int() function checks if a given value is of the integer type.
It returns true if the value is an integer, and false otherwise.

The integer type represents a data type used to express numeric values without decimal points.
In PHP, although strings and floating-point numbers can be treated as numbers depending on the context, the integer type itself only contains whole numbers without decimal points.

Basic Example

PHP 
/* Integer type */
var_dump(is_int(1));          // bool(true)
var_dump(is_int(0));          // bool(true)
var_dump(is_int(-10));        // bool(true)

/* Floating-point numbers (float) */
var_dump(is_int(1.0));        // bool(false)
var_dump(is_int(0.0));        // bool(false)
var_dump(is_int(3.14));       // bool(false)

/* Strings */
var_dump(is_int('1'));        // bool(false)
var_dump(is_int('0'));        // bool(false)
var_dump(is_int('10'));       // bool(false)

/* Results of numeric operations */
var_dump(is_int(1 + 1));      // bool(true)
var_dump(is_int(10 / 2));     // bool(true)
var_dump(is_int(9 / 2));      // bool(false)

/* Type casting */
var_dump(is_int((int) '1'));  // bool(true)
var_dump(is_int((int) 1.9));  // bool(true)

Note:
The gettype() function returns the data type of the given value as a string.

Syntax

PHP 
is_int(mixed $value): bool

Parameters

Description of the is_int() function parameters
$value Required. The value to be checked for the integer type.

Return Values

If the value passed as a parameter is of the integer type, the function returns true; otherwise, it returns false.

Things to Keep in Mind

There are several important points to be aware of when using the is_int() function.

Numeric Strings Such as '1' Return false

PHP 
$num = '10';

var_dump(is_int($num)); // bool(false)

Floating-Point Numbers Such as 10.5 Return false

PHP 
$num_1 = 10.5;
$num_2 = 10.0;

var_dump(is_int($num_1)); // bool(false)
var_dump(is_int($num_2)); // bool(false)

Integers That Start with 0, Such as 0123, Return true

PHP 
$num_1 = 0123;
$num_2 = -0123;
$num_3 = 000;

var_dump(is_int($num_1)); // bool(true)
var_dump(is_int($num_2)); // bool(true)
var_dump(is_int($num_3)); // bool(true)

Practical Examples

The is_int() function is useful in situations where you need to check whether a value is of the integer type.

Checking Whether a Variable Is an Integer

When you need to determine whether a variable is an integer, using the is_int() function helps keep your code concise and clear. For example, the following code checks whether a variable is of the integer type and performs different actions accordingly.

PHP 
$a = '2';

if (is_int($a)) {
    echo 'Variable a is of the integer type.';
} else {
    echo 'Variable a is not of the integer type.';
}

// Output: 'Variable a is not of the integer type.'

As shown in the next example, when you need to verify whether a value retrieved from a database is an integer, you can write your code as follows.

PHP 
$value = $db->query('SELECT value FROM table WHERE id = 1')->fetchColumn();

if (!is_int($value)) {
    echo 'The data type is not valid.';
    exit;
}

// ... remaining processing

Input Validation

You can use this function to check whether a value entered by a user is an integer. For example, when receiving an age value from a form, you can write code like the following.

PHP 
$user_input = $_POST['user_input'];

if (is_int($user_input)) {
    // Handle valid integer input
} else {
    // Handle invalid input
}

Performing Calculations

Before performing calculations that only allow integer values, you can use is_int() to validate the input. For example, when adding two numbers, you can write code as follows.

PHP 
$num1 = 10;
$num2 = 20;

if (!is_int($num1) || !is_int($num2)) {
    echo 'Addition can only be performed on integers.';
    exit;
}

$sum = $num1 + $num2;

echo "The sum of the two numbers is {$sum}.";
// Output: 'The sum of the two numbers is 30.'

References

See also