php exceeds the shaping range

Most programming languages ​​have limitations on variable types. Exceeding these limits will cause running problems or errors, and PHP is no exception. In PHP, the range of integer variables is -2147483648 to 2147483647. When this range is exceeded, the problem of exceeding the integer range will occur.

There may be many reasons for exceeding the range of the integer type, such as:

1. Number operation exceeds the range. When adding two integers, if their sum exceeds the maximum value of the integer type, an out-of-range problem will result.
2. Integer overflow problem. Another common reason for exceeding the range of an integer type is that the value of the variable itself exceeds the maximum value of the integer type. This is called integer overflow.
3. When reading data from other systems or interfaces, the data types are inconsistent.

In order to better understand the problem of PHP exceeding the integer range, we can illustrate it through the following example.

1. Number operation out of range

For example, let us try to calculate the sum of two integers so that the result is outside the range of the integer type.

$x = 2147483647;
$y = 2;

echo $x $y; // The output result is -2147483647

Due to $x and $y The added result exceeds the maximum value of 2147483647, so PHP treats it as a negative number and outputs the result as -2147483647.

2. Integer overflow

You can also manually set the integer variable to a value greater than 2147483647 to reproduce the integer overflow problem.

$x = 2147483648;

echo $x; //The output result is -2147483648

Because 2147483648 is greater than the largest integer value 2147483647, PHP treats it as a negative number -2147483648.

3. Inconsistent data types

When reading data from other systems or interfaces, you need to pay attention to the problem of inconsistent data types.

For example, let us get a numerical data from a json file.

{"number": 12345678901234567890}

$json = file_get_contents("/path/to/json/file.json");
$data = json_decode($json, true );
$number = $data["number"];

echo $number; //The output result is 12345678901234567890

Since the maximum integer value in PHP is 2147483647, and reading If the value in the json file is greater than this value, PHP will treat it as a float instead of an integer.

Regarding how to solve the problem that PHP exceeds the integer range, there are the following solutions:

1. Use a large number library. When you need to perform calculations beyond the range of integers, you can use the large number library provided by PHP, such as gmp or bcmath.

For example:

$x = "12345678901234567890";
$y = "9876543210987654321";

$sum = gmp_add($x, $y );
echo gmp_strval($sum); // The output result is: 22222222112222222211

2. Store integers in the database instead of using php variables. Database storage can accommodate larger integer values.
3. Modify the php configuration file. You can try to modify the configuration items in the php configuration file php.ini, such as setting the use of 64-bit integers.

In PHP development, exceeding the range of integers is a problem that cannot be ignored. Special attention needs to be paid during code writing and code review to prevent such problems from occurring.

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