PHP round() Function

Introduction

In PHP, the round() function is a built-in mathematical function that allows you to round a number to a specified precision or decimal place. It provides a convenient way to manipulate and format numerical values based on your specific requirements.

The round() function takes two parameters: the number to be rounded and an optional precision value. The precision determines the number of decimal places to which the given number should be rounded. If no precision is specified, the function rounds the number to the nearest integer.

The round() function follows standard rounding rules. If the fractional part of the number is less than 0.5, it is rounded down to the nearest whole number. If the fractional part is equal to or greater than 0.5, it is rounded up to the nearest whole number.

The round() function is particularly useful in scenarios where you need to display numbers in a specific format, such as currency or percentage values. By specifying the desired precision, you can ensure that numbers are rounded correctly and displayed with the appropriate level of accuracy.

In addition to rounding numbers, the round() function can also be used in mathematical calculations, data manipulation, and formatting operations. It is a versatile tool that helps ensure consistency and accuracy when working with numerical values in PHP.

Syntax of round() in PHP

The syntax of the round() function in PHP is as follows:

The round() function accepts three parameters:

• $number(required): This parameter represents the numeric value that you want to round. It must be a float or a numeric value that can be implicitly converted to a float.
• $precision (optional): This parameter specifies the number of decimal places to which you want to round the number. It is an integer value and defaults to 0 if not specified. Negative precision values are also allowed, which means rounding to the nearest ten, hundred, etc.
• $mode(optional): This parameter determines the rounding mode to be used if the number falls exactly between two possible rounded values. It is an integer value and defaults to PHP_ROUND_HALF_UP. Other rounding modes include PHP_ROUND_HALF_DOWN, PHP_ROUND_HALF_EVEN, and PHP_ROUND_HALF_ODD.

Run the above code in your editor for a better and clear explanation.

Parameter Values of round() in PHP

The round() function in PHP accepts three parameters: $number, $precision, and $mode.

Let's explore each parameter and its possible values:

$number (required):

• This parameter represents the numeric value that you want to round.
• It can be a float or a numeric value that can be implicitly converted to a float.

$precision (optional):

• This parameter specifies the number of decimal places to which you want to round the number.
• It is an integer value and defaults to 0 if not specified.
• Positive values indicate rounding to that number of decimal places.
• Negative values indicate rounding to the nearest ten, hundred, etc.
• Zero means rounding to the nearest whole number.

$mode (optional):

• This parameter determines the rounding mode to be used if the number falls exactly between two possible rounded values.
• It is an integer value and defaults to PHP_ROUND_HALF_UP.
• The available rounding modes are:
• PHP_ROUND_HALF_UP: Round up if the number is halfway between two values.
• PHP_ROUND_HALF_DOWN: Round down if the number is halfway between two values.
• PHP_ROUND_HALF_EVEN: Round to the nearest even number if the number is halfway between two values.
• PHP_ROUND_HALF_ODD: Round to the nearest odd number if the number is halfway between two values.

Run the above code in your editor for a better and clear explanation.

Return Value of round() in PHP

The round() function in PHP returns the rounded value as a float. The returned value represents the result of rounding the input number according to the specified precision and rounding mode.

Here's an example to demonstrate the return value of round():

Output:

In this example, the round() function is applied to the number 3.14159 with a precision of 2 decimal places. The returned value, stored in the variable $roundedNumber, is 3.14. This rounded value, as a float, is then displayed using the echo statement.

It's important to note that the return value is a float, even if the input number and precision are integers. The float type is used to accommodate decimal values resulting from the rounding operation. Run the above code in your editor for a better and clear explanation.

PHP Version

The round() function is available in all versions of PHP, including PHP 4, PHP 5, PHP 7, and beyond. It is a core PHP function, so you don't need to install any additional extensions or libraries to use it.

Whether you are using PHP 5.x or PHP 7.x, you can utilize round() to perform rounding operations on numeric values.

Here's an example of using round() in PHP:

Output

Regardless of the PHP version you are using, this code snippet will produce the same result: 3.14. The round() function has remained consistent in terms of its functionality and usage across different PHP versions. Run the above code in your editor for a better and clear explanation.

PHP Changelog

The above is the PHP change of the round() function:

• PHP 4.0.0: The round() function was introduced as part of the PHP core, providing the capability to round numbers to the nearest integer or a specified number of decimal places.
• PHP 4.2.0: Fixed a bug in the round() where negative values with a precision of 0 were incorrectly rounded up instead of down.
• PHP 5.2.7, PHP 5.3.0: Fixed a bug in the round() where certain values could produce incorrect results due to floating-point precision issues.
• PHP 5.3.0: Added the $mode parameter to round(), allowing developers to specify the rounding mode for cases where the number is exactly halfway between two possible rounded values. The available rounding modes are PHP_ROUND_HALF_UP, PHP_ROUND_HALF_DOWN, PHP_ROUND_HALF_EVEN, and PHP_ROUND_HALF_ODD.
• PHP 5.4.0: The $mode parameter of round() now defaults to PHP_ROUND_HALF_UP if not explicitly provided. Previously, it defaulted to PHP_ROUND_HALF_DOWN.
• PHP 7.2.0: Fixed a bug in the round() where certain numbers were rounded incorrectly due to a precision issue with large values.
• PHP 8.0.0: The round() function now correctly handles edge cases involving extremely large or small numbers, producing more accurate and consistent results.

Advantages of Using Round in PHP

Using the "round()" function in PHP offers several advantages that make it a valuable tool for working with numerical values. Here are some advantages of using the "round()" function:

• Precision Control: The "round()" function allows you to control the precision or decimal places to which a number should be rounded. This is particularly useful when working with financial data or any scenario where accuracy and precision are crucial. You can specify the desired precision to ensure consistent and accurate rounding of numbers.
• Consistent Rounding Rules: The "round()" function follows standard rounding rules, which helps maintain consistency in your calculations and data manipulation. It rounds numbers based on the value of the fractional part, ensuring that the rounding behaviour is predictable and consistent across different use cases.
• Flexible Formatting: The "round()" function enables you to format numbers according to your specific requirements. You can round numbers to integers or specific decimal places, which is useful when displaying values in a particular format, such as currency, percentage, or measurement units. This flexibility ensures that your numeric output is appropriately formatted and presented to users or other parts of your application.
• Mathematical Calculations: The "round()" function can be utilized in various mathematical calculations. It allows you to round the results of mathematical operations to the desired precision, helping to maintain the necessary level of accuracy in your calculations. Whether it's addition, subtraction, multiplication, or division, the "round()" function ensures that the calculated results are rounded correctly.
• Data Consistency: When working with data that involves rounding, using the "round()" function helps maintain data consistency throughout your application. By rounding numbers consistently and accurately, you can avoid discrepancies or errors that may arise from using different rounding methods or relying on default rounding behaviour.
• Improved Readability: By explicitly using the "round()" function, your code becomes more readable and self-explanatory. It communicates your intention to round a specific number to a particular precision, making it easier for other developers to understand and maintain your code.
• Internationalization Support: The "round()" function takes into account the locale settings of your PHP environment. This means that it can adapt to different number formatting conventions based on the locale, ensuring that your rounded numbers are displayed in a way that is appropriate for the given language or region.

Overall, the "round()" function in PHP provides advantages in terms of precision control, consistent rounding rules, flexible formatting, mathematical calculations, data consistency, code readability, and internationalization support. It is a useful tool for working with numerical values, ensuring accuracy and maintaining data integrity in various scenarios within your PHP applications.

Examples of round() in PHP

Round Numbers to Three Decimals

Output

In this example, we start with the number 3.14159. We use the round() function to round it to three decimal places, resulting in 3.142. To ensure that the output is formatted with exactly three decimal places, we then use the number_format() function, specifying a precision of 3. The resulting formatted number, 3.142, is then displayed using the echo statement. Run the above code in your editor for a better and clear explanation.

Round Numbers Using the Constants

Output

In this example, we start with the number 3.14159. We use the round() function with a precision of 3 and the PHP_ROUND_HALF_UP constant to round the number up to three decimal places, resulting in 3.142. To ensure that the output is formatted with exactly three decimal places, we then use the number_format() function, specifying a precision of 3. The resulting formatted number, 3.142, is then displayed using the echo statement. Run the above code in your editor for a better and clear explanation.