php Determine a float variable has two decimal places

Question

MySQL data imoprt mongo database.

price float(15,2) in mysql, mongo is not float(15,2).

I want to Determine a var $price have two decimal places.

eg. 100.00 is right, 100 or 100.0 is wrong.

eg.1

$price = 100.00;

$price have two decimal, it's right.

eg.2

$price = 100.0;

$price have not two decimal, it's wrong.

Answer 1

I like to use Regular Expressions to do these things

function validateTwoDecimals($number)
{
   if(preg_match('/^[0-9]+\.[0-9]{2}$/', $number))
     return true;
   else
     return false;
}

(Thanks to Fred-ii- for the corrections)

Answer 2

Everybody is dancing around the fact that floating point numbers don't have a number of decimal places in their internal representation. i.e. in float 100 == 100.0 == 100.00 == 100.000 and are all represented by the same number, effectively 100 and is stored that way.

The number of decimal places in this example only has a context when the number is represented as a string. In which case any string function that counts the number of digits trailing the decimal point could be used to check.

Answer 3

number_format($price, $numberOfDecimalDigits) === $price;

or

strrpos($price, '.') === strlen($price) - 1 - $numberOfDecimalDigits;

Trivia: $price should not be called a "float variable". This is a string that happens to represent a float value. 100.00 as a float has zero decimal digits, and 100.00 === 100 as float :

$price = 100.00;
echo $price; // output: 100
$price2 = (float)100;
echo $price === $price2; // ouput: 1

Answer 4

In order for this to work, the number will need to be wrapped in quotes.

With the many scripts I've tested, using $price = 100.00; without quotes did not work, while $price = 100.10; did, so this is as best as it gets.

<?php 
$number = '100.00';
echo $number.'<br>';
$count = explode('.',$number);

echo 'The number of digits after the decimal point is: ' . strlen($count[1]);

if(strlen($count[1]) == 2){
echo "<br>";
echo "There is 2 decimal points.";
}

else{
echo "<br>";
echo "There is not 2 decimal points.";
}

Answer 5

After you format the value, you can check with simply splitting the value as string into 2 parts, for example with explode ...

$ex=explode('.',$in,2); if (strlen($ex[1])==2) 
{
 // true
}
else
{
 // false
}

But again, as i've commented already, if you really have floating input, this is just not a reliable way, as floating numbers are without set decimal places, even if they appears so because of the rounding at the float=>string conversion

What you can do, if you really have floating numbers and wish to have xxx.yy format numbers:

1) convert float to string using round($x,2), so it will round to 2 decimal places. 2) explode the number as i've described, and do the following:

while (strlen($ex[1]<2)) {$ex[1].='0';}
$number=implode('.',$ex);

Answer 6

I would use the following function for that:

function isFloatWith2Decimals($number) {
    return (bool) preg_match('/^(?:[1-9]{1}\d*|0)\.\d{2}$/', $number);
}

This will also check if you have only one leading 0 so number like 010.23 won't be considered as valid whereas number like 0.23 will.

And if you don't care about leading 0 you could use simpler method:

function isFloatWith2Decimals($number) {
    return (bool) preg_match('/^\d+\.\d{2}$/', $number);
}

Of course numbers need to be passed as string - if you pass 100.00 won't be considered as true, whereas '100.00' will