How can one check in PHP if a string can be converted into a whole number?

Question

For instance, "000", "404", and "0523" can be converted into whole numbers in PHP, but "42sW" and "423 2343" cannot be converted into whole numbers.

Are you looking for something more than just checking that every character in the string is a digit? — John3136, Feb 24 '12 at 04:09
[Which definition of whole number](https://en.wikipedia.org/wiki/Whole_number) are you thinking of? — icktoofay, Feb 24 '12 at 04:11

score 21 · Accepted Answer · edited Aug 08 '17 at 21:48

21

Use the ctype_digit function. is_numeric will also permit floating point values.

$numArray = array("1.23","156", "143", "1w");
foreach($numArray as $num)
{
    if (ctype_digit($num)) {
            // Your Convert logic
        } else {
            // Do not convert print error message
        }
    }
}

edited Aug 08 '17 at 21:48

Ken Wayne VanderLinde

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answered Feb 24 '12 at 08:19

Naveen Kumar

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Thanks, `ctype_digit` works great. `is_numeric` doesn't work since all rational numbers will work for is_numeric, but it's nice to know that function too, thanks! – dangerChihuahua007 Feb 24 '12 at 18:32
@gus What are you trying to say. – Naveen Kumar Mar 05 '12 at 09:23
1

If you do pass in int it will return false regardless if its a whole number. That may not be expected. Thought it worth mentioning, cheers. – gus Mar 05 '12 at 10:05
1

$numArray = array("1.23",156, "143", "1w"); 1.23 false *156 false* 143 true 1w false – gus Mar 05 '12 at 14:48
@David Faux: 1.2e2 is a "whole number" but will will fail the ctype,_digit() test. – symcbean Aug 08 '17 at 22:36

score 9 · Answer 2 · answered Feb 24 '12 at 04:10

9

PHP's is_numeric() can determine if a given param is a number or a number string. Have a read through the manual for some examples.

answered Feb 24 '12 at 04:10

Russell Dias

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This will be true for things like '1.5' – galdikas Sep 07 '16 at 06:18

score 2 · Answer 3 · answered Feb 24 '12 at 04:09

2

ctype_digit should be what you're looking for.

answered Feb 24 '12 at 04:09

icktoofay

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score 2 · Answer 4 · answered Feb 24 '12 at 04:22

2

42Sw can be converted to a number by using intval()

      echo intval("42sW"); // prints 42

answered Feb 24 '12 at 04:22

gus

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score 1 · Answer 5 · answered Feb 24 '12 at 04:10

1

use is_numeric():

if (is_numeric("string")) {
    echo "This can be converted to a number";
}

answered Feb 24 '12 at 04:10

fardjad

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1

This will be true for things like '1.5' – galdikas Sep 07 '16 at 06:19
@galdikas and? isn't 1.5 a number? – clockw0rk Jun 15 '23 at 03:55
@clockw0rk depending on the use case it might be ok or not. I did have once a case where I specifically needed to determine if a string is integer. – galdikas Jun 15 '23 at 12:05

score 0 · Answer 6 · answered Feb 24 '12 at 04:11

0

You could try something like this.

<?php
if (is_numeric($string)) {
//functions here
}
else{
//functions2 here
}
?>

answered Feb 24 '12 at 04:11

ionFish

1,004
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1

This will be true for things like '1.5' – galdikas Sep 07 '16 at 06:19

score 0 · Answer 7 · answered Feb 24 '12 at 04:12

0


$test = "42sW";
if (ctype_digit($test)) {
        echo "The string $test consists of all digits.\n";
    } else {
        echo "The string $test does not consist of all digits.\n";
    }

//OR
is_numeric($test);   // false

answered Feb 24 '12 at 04:12

Sudhir Bastakoti

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1

Wouldn't `is_numeric()` return true for non-whole numbers as well (1.23)? – jprofitt Feb 24 '12 at 04:20

How can one check in PHP if a string can be converted into a whole number?

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