String to integer conversion in PHP changes the value

Question

So I have this simple code:

$var = abs(crc32('string - 8 characters')).rand(100,999);
var_dump($var);
echo '<br>';
var_dump((int)$var);
echo '<br>';
var_dump(intval($var));

And the result:

string(13) "2047654753402"
int(2147483647)
int(2147483647)

Why the integer value is 2147483647? I expected it to be 2047654753402. I just want to convert the string to integer without changing the value.

Considering that your integer is a signed 32-bit integer..... what do you expect to happen when your string value is outside of that range? There's even a whole page of the PHP Documents that explains what happens when you have an integer overflow - php.net/manual/en/language.types.integer.php — Mark Baker
– Mark Baker, Commented May 30, 2016 at 17:19
If you need to work with integers that size, switch to 64-bit PHP — Mark Baker
– Mark Baker, Commented May 30, 2016 at 17:21
Why the integer value is 2147483647? Because 2147483647 is the maximum value that can be stored in a 32-bit signed integer — Mark Baker
– Mark Baker, Commented May 30, 2016 at 17:30

Tony · Accepted Answer · 2016-05-30 17:40:20Z

1

You can not convert large string number to integer because interger has limitation -2147483647 to 2147483647. So If you want to convert number string to integer which has out of range of integer length, you can use double.

$var = abs(crc32('string - 8 characters')).rand(100,999);
var_dump($var);
echo '<br>';
var_dump((double)$var)

answered May 30, 2016 at 17:40

Tony

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5 Comments

Mark Baker Over a year ago

If you're recommending this as a solution, it might be worth noting that it will likely result in some loss of precision

Qrzysio Over a year ago

What's wrong with this solution? I just want to be able to put this long number into database in BIGINT column. This (double) returns a float number. Will it be correct to put it into BIGINT?

Mark Baker Over a year ago

What's wrong with this solution? What's wrong is potential lack of precision..... try running

$var = abs(crc32('string - 8 characters')).rand(100,999); var_dump($var); $var2 = (double)$var; var_dump($var2); $var3 = (string)$var2; var_dump($var3);

and see if $var3 is the same as $var

Qrzysio Over a year ago

Well, I've checked on 3 different servers and $var3 returns exactly the same result as $var.

Mark Baker Over a year ago

@Qrzysio - That's not guaranteed when the value is larger than PHP_INT_MAX.... it can also be affected by the precision setting in your php.ini file

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