What is the usage of the round function in PHP?

The round() function in PHP is used to round a floating-point number to the nearest integer.

Syntax of functions:

round(float $number, int $precision = 0, int $mode = PHP_ROUND_HALF_UP): float|int

Explanation of parameters.

1. $number: A floating-point number that must be rounded to the nearest whole number.
2. $precision: Optional, can specify the number of decimal places, default is 0, indicating rounding to the nearest whole number.
3. $mode: Optional parameter that specifies the rounding mode, defaulting to PHP_ROUND_HALF_UP, which means rounding up. Other optional modes include PHP_ROUND_HALF_DOWN (rounding down), PHP_ROUND_HALF_EVEN (rounding up if the discarded part is 0.5 and the previous digit is odd, rounding down if it’s even), and PHP_ROUND_HALF_ODD (rounding up if the discarded part is 0.5 and the previous digit is even, rounding down if it’s odd).

Return value: the rounded result, in either floating-point or integer type.

“Could you please explain this to me one more time?”

echo round(3.4);  // 输出：3
echo round(3.5);  // 输出：4
echo round(3.6);  // 输出：4

echo round(3.14159, 2);  // 输出：3.14，保留两位小数
echo round(3.14559, 2);  // 输出：3.15，保留两位小数

echo round(3.5, 0, PHP_ROUND_HALF_DOWN);  // 输出：3，向下舍入
echo round(3.5, 0, PHP_ROUND_HALF_EVEN);  // 输出：4，根据奇偶性舍入

Note: The results returned by the round() function may not always be accurate, due to the way floating-point numbers are represented in computers. For more precise calculations, consider using other related functions such as number_format() or functions within the bcmath extension.