The floor() function in PHP rounds a number down to the nearest integer. This means it will take a floating-point number and return the largest integer that is less than or equal to that number.

Syntax:

floor(float $number): float

• $number: The floating-point number you want to round down.
• Return Value: Returns the largest integer less than or equal to the input number, as a float.

Example 1: Rounding Down a Positive Decimal

<?php
echo floor(4.7);
?>

Output:

4

Explanation: The number 4.7 is rounded down to the nearest integer, which is 4.

Example 2: Rounding Down a Positive Decimal Close to the Next Integer

<?php
echo floor(7.9);
?>

Output:

7

Explanation: 7.9 is rounded down to 7, which is the largest integer less than 7.9.

Example 3: Rounding Down a Negative Decimal

<?php
echo floor(-3.4);
?>

Output:

-4

Explanation: For negative numbers, floor() rounds down towards negative infinity. Therefore, -3.4 rounds down to -4.

Example 4: Rounding Down an Integer

<?php
echo floor(5);
?>

Output:

5

Explanation: If the input is already an integer (like 5), the function returns the same integer without any changes.

Example 5: Rounding Down Zero

<?php
echo floor(0);
?>

Output:

0

Explanation: The number 0 remains 0 because it is already the nearest integer.

Key Points:

• The floor() function always rounds down to the nearest integer.
• It returns the result as a float, even though the value is an integer.
• It works with both positive and negative numbers.
• It is particularly useful in scenarios where you need to ensure that a number does not exceed a certain threshold, such as when calculating items per page in pagination or when determining the number of full units you can fit into a given quantity.

In summary, floor() is a straightforward yet powerful function for rounding down numbers in PHP.