Minimum integer in PHP 7

Question

In interactive mode on PHP 7 (64 bit Ubuntu),

php > echo true;
1
php > echo false; # no output for false
php > echo PHP_INT_MIN == -9223372036854775808;
1
php > echo is_int(PHP_INT_MIN);
1
php > echo is_int(-9223372036854775808);

Why doesn't the last line output 1?

Ok echo PHP_INT_MIN === -9223372036854775808; is false. Nonetheless, echo PHP_INT_MIN; displays -9223372036854775808 and echo is_int(-9223372036854775808); is false — zuggy
– zuggy, Commented May 12, 2017 at 17:39
Sorry I'm wondering why the value displayed by PHP_INT_MIN does not appear to be an integer when checking with is_int() — zuggy
– zuggy, Commented May 12, 2017 at 17:40

Sammitch · Accepted Answer · 2017-05-12 17:48:17Z

3

var_dump() is your friend.

var_dump(
    PHP_INT_MIN,
    is_int(PHP_INT_MIN),
    -9223372036854775808,
    is_int(-9223372036854775808)
);

/* Output:
int(-9223372036854775808)
bool(true)
float(-9.2233720368548E+18)
bool(false)
*/

answered May 12, 2017 at 17:48

Sammitch

32.5k7 gold badges57 silver badges92 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Community · Accepted Answer · 2020-06-20 09:12:55Z

3

Because is_int :

perates in signed fashion, not unsigned, and is limited to the word size of the environment php is running in.

and so -9223372036854775808 it's smaller than your system word bound

edited Jun 20, 2020 at 9:12

CommunityBot

11 silver badge

answered May 12, 2017 at 17:58

Riccardo Bonafede

6061 gold badge9 silver badges17 bronze badges

2 Comments

zuggy Over a year ago

Thanks for pointing this out. Would have accepted this as an answer had I not done so already

Code4R7 Over a year ago

The comment you cite from the PHP.net comments looks invalid in PHP7 to me, as integers can be signed. (See my answer)

Code4R7 · Accepted Answer · 2017-05-14 18:40:04Z

2

First PHP parses your integer value as float, because of an integer overflow. Then it uses is_int() to determine if what PHP has parsed is an integer. See example #3 for 64-bit systems.

Please note that is_int() does work with unsigned integers as well. Using 32-bit PHP 7:

echo PHP_INT_MIN;                    // -2147483648
echo var_dump(is_int(-2147483648));  // bool(false)
echo var_dump(is_int(-2147483647));  // bool(true)

To make sure PHP_INT_MIN is off by one, please try this on your 64-bit PHP 7:

echo var_dump(is_int(-9223372036854775807));  // bool(true)?

If you need more integer precision, you could use the GMP extension.

edited May 14, 2017 at 18:40

answered May 12, 2017 at 18:04

Code4R7

3,1521 gold badge24 silver badges46 bronze badges

Collectives™ on Stack Overflow

Minimum integer in PHP 7

3 Answers 3

Comments

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related