Why doesn't php round to one decimal place?

Method: 1. Use the "*" operator to expand the decimal by 10 times. The syntax "$a=decimal*10;" moves the decimal point backward one place; 2. Use floor() to expand the decimal The decimal is rounded down and the decimal part is discarded, the syntax is "$b=floor($a);"; 3. Divide the rounded number by 10, the syntax is "$c=$b/10;".

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

php reserves one digit Decimal (not rounded) method

For example, 3.1625 takes 1 decimal place, and the last digit cannot be rounded. Result: 3.1.

In PHP, you can use the floor function to achieve one decimal place without rounding.

The floor function uses rounding.

For example, floor(4.66456) Result: 4; floor(9.1254) Result 9.

Therefore, to remove 1 decimal place, you need to multiply by 10 first, then round off, and then divide by 10, that is:

$a=小数*10;
$b=floor($a);
$c=$b/10;

is directly simplified to:

floor(小数*10)/10

Example:

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);   
echo (floor(3.1625*10)/10)."<br>";
echo (floor(0.5985*10)/10)."<br>";
echo (floor(1.1425*10)/10)."<br>";
?>

Extended knowledge: Method of retaining several decimal places (rounding)

1. round function

round(小数，保留位数)

2. The sprintf function

sprintf("%01.位数值f", 小数)

implements rounding, and if it does not have decimal places, it will automatically use the specified character (specified 0) to fill in the specified decimal places

echo sprintf("%01.2f", 5.228);  //  5.23
echo sprintf("%01.2f", 5.224);  //  5.22
echo sprintf("%01.2f", 5);      //  5.00

3, number_format function

number_format(小数，保留位数)

If it does not have a decimal place, it will automatically fill it with 0 to the specified decimal place

echo number_format(5.228,2);    //  5.23
echo number_format(5.224,2);    //  5.22
echo number_format(5,2);        //  5.00

Recommended learning: "PHP Video tutorial》

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