在PHP中的十进制数字中的某个点之后有没有办法正则表达式和删除？ [重复]

Question

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• PHP How do I round down to two decimal places? 16 answers

Is there any way to do a regex that cuts off a number at a certain point without rounding (simply drops the digits?) say after 4 digits.... It will not be handling negative numbers, EVER. I could have number inputs such as 0.03123 or 1.31, or 10000.98, etc .... What I have written so far as my solution is rounding and not what I'm seeking....

$number = 10000.51999999;
$precision = 4;
echo "<br>";

// grab number before decimal by rounding down the whole number down...
$numberBeforeDecimal = floor($number); 
echo "<br>";

// grab the decimal and set the correct precision needed
$n = $number;
intval($n); // 12
$theDecimalPart = explode('.', number_format($n, ($precision)))[1]; // 3430

echo $theDecimalPart; // this is outputting 5200

$theNewValue = $numberBeforeDecimal.".".$theDecimalPart;

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Answer 1

• explode() the number to get integer and decimal part separated out in an array
• Use substr() function to get relevant precision from the decimal part.
• Finally, concatenate them back.

Try the following (Rextester DEMO):

$number = 10000.51999999;
$precision = 4;

// separate out the integer and decimal part
$number_str_arr = explode('.', $number);

// concatenate them back
$theNewValue = $number_str_arr[0] . '.' . substr($number_str_arr[1], 0, $precision);
echo $theNewValue; // displays 10000.5199