The floor() function in PHP is used to round a floating-point number down to the nearest whole integer (toward negative infinity).

Syntax:

float floor ( float $value )

• $value: The input number you want to round down.

How it Works:

• It takes a number and returns the largest integer less than or equal to that number.

Example 1: Basic Usage

<?php
echo floor(4.7);  // Outputs: 4
echo floor(4.3);  // Outputs: 4
?>

Explanation:

• 4.7 and 4.3 both get rounded down to 4.

Example 2: Negative Numbers

<?php
echo floor(-4.3);  // Outputs: -5
echo floor(-4.7);  // Outputs: -5
?>

Explanation:

• With negative numbers, floor() moves "down" the number line, so -4.3 goes to -5 (more negative).

Example 3: Using with Calculations

<?php
$price = 9.99;
$discount = 0.15;

$finalPrice = floor($price - ($price * $discount));
echo $finalPrice; // Outputs: 8
?>

Explanation:

• After applying the discount, the price is 8.4915. floor() rounds it down to 8.

When to Use:

• When you need to ensure values are rounded down for things like:
  • Pagination calculations.
  • Pricing where you can't exceed a certain threshold.
  • Trimming decimal points without rounding up.