round() function returns the rounded value of x to the specified precision. If no precision specified, it will round all the decimals.
   float round(float value [, int precision = 0, int mode = PHP_ROUND_UP])

<?PHP
	echo round(3);  //3
	echo round(3.2);  //3
	echo round(3.5);  //4
	echo round(3.2436);  //3	
?>

Specify the precision of the returned value. It can be negative.

<?PHP
   echo round(3.1415926, 2); //3.14
   echo round(3.1415926, 4); //3.1416 
   echo round(3.2436, -2);  //0
   echo round(32436, -2);  //32400
?>

The final several decimals may be 0, and it can be deleted.

<?PHP
	$x = 5.245999;
	$y = round($x, 4); //y=5.2460

	if (floor($x) != $x)
	{
		$x = round($x,4);
		$x = preg_replace("/0+$/","",$x);
		$x = preg_replace("/\.$/","",$x);  //x=5.246
	}
?>

round() do not support number with commas. number_format() can be used to format number. Or just replace the commas with string functions.

<?PHP
	$num = 43592585.3429;
	$num2 = number_format($num)
	echo $num2;  //43,592,585
	echo number_format($num2, 0, ".", "");  //43592585
	
	$num = "43,592,585.3429";
	$num = str_replace(",","",$num);
	echo "$num"; //43592585.3429
?>

There are three modes: