Topic: Checking for a whole number.

[tjmbc]

I need to check to see if this is a whole number...
 
   $num_in / 5

[GingerRobot]

Use the modulus operator:


if($num_in % 5 == 0){
    echo 'Multiple of 5';
}else{
    echo 'Not a multiple of 5';
}

[btherl]

The input will need to be an integer for that to work .. as long as it is, it should be fine.

[deadonarrival]

Code: [Select]

$answer = $num_in / 5;
if(is_int($answer))
{
 #integer
}
else
{
 #not an integer
}

[Barand]

@doa,

if $num_in = 10.00, then you get "not an integer" as the answer is a float (2.00)

[deadonarrival]

Hmm, didn't know that one. Ignore my suggestion then

[Barand]

I must admit, I had to test your code to make sure. You never know, it might catch on.

[deadonarrival]

I would have thought it would make sense for is_int to check whether the number is a whole number, regardless of variable type. Or have a seperate function to check if the VALUE is an integer, rather than the TYPE.

Modulus never seems to work correctly for me, it's temperomental

[The Little Guy]

$myNumber = 23.23;
if(is_float($myNumber))
     echo 'this is a float number';
else
     echo 'this is not a float number';

[btherl]

DOA, it does make sense to have a function that checks for integerness even if the value is not an integer, but is_int() isn't that function

If you write such a function you will have to decide what to do about large floats, which typically aren't integers even if they should be integers, due to floating point innacuracy.

[deadonarrival]

Yarp, but that's a problem I can never solve myself

Anyway, modulus is the answer to the original question - and binary inaccuracy is something we can keep for another day's musing

[DarkWater]

Or without calling any functions, you could do:

$num = $firstnumber / 2;
if ($num == (int) $num) {
 //It's whole
}
else {
 //It's not
}

[Barand]

It still doesn't allow for floating point inaccuracies. You can't depend on equality tests with FP values.

eg your number may be stored as 5.000000001, in which case you need to test if the difference is within tolerable bounds

Code: [Select]

if (abs($num - (int)$num) < 0.000001)

[hitman6003]

Perhaps some examples will help?

Code: [Select]

<?php

$a['int'] =  (int) 4;
$a['float_but_int'] = (float) 4.00;
$a['normal_float'] = (float) 4.1;
$a['small_float'] = (float) 4.0000000000001;
$a['negative_float'] = (float) -5.00004;

foreach ($a as $name => $value) {
echo $name . "'s value is: " . $value . "\n";

if (is_int($value)) {
echo $name . " is an integer.\n";
}

if (is_float($value)) {
echo $name . " is a float.\n";
}

if ($value - floor($value) == 0) {
echo $name . " was determined to be a whole number (integer).\n";
}

if ($value - floor($value) != 0) {
echo $name . " was determined not to be a whole number (float).\n";
}

echo str_repeat("-", 25) . "\n";
}
By subtracting floor($value) from $value and seeing if there is a remainder, you can determine if it's a whole number.

[corbin]

hitman6003, I'm not positive, but I think that you may still have floating point innaccuracies with that....