Comparison of long numeric strings

Comparison of long numeric strings. This post was last edited by anyilaoliu at 15:04:43, January 13 ,.

Example
This problem occurs.

$a = "222111565652521142";$b = "222111565652521139";$c = 222111565652521142;$d = 222111565652521139;var_dump($a);echo "
";var_dump($b);echo "
";var_dump($c);echo "
";var_dump($d);echo "
";if ($a == $b) {echo 3;}else{echo 31;}echo "
";if ($c == $d) {echo 4;}else{echo 41;}echo "
";

The result is

string '222111565652521142' (length=18)string '222111565652521139' (length=18)float 2.2211156565252E+17float 2.2211156565252E+17314

The question is, how can we compare the two in the second case?

Problem 2: The two groups of numbers read from the database are displayed as string (18) after var_dump, but the comparison result is the opposite of the above example, the comparison between the two strings is also passed.

Solution

Reply to discussion (solution)

The integer with a length of more than 11 characters must be processed as a string.
The characteristics of floating point cannot be used in scenarios with high precision requirements.

The integer with a length of more than 11 characters must be processed as a string.
The characteristics of floating point cannot be used in scenarios with high precision requirements.

I learned this.

In addition, I tried again today and found that two 18-bit Arabic numbers in string format in my environment, the = operator will still ignore the last two digits, it should have been converted internally.

This problem does not occur in another environment. the Two Strings can use the = operator correctly according to the string.

Ask about settings or extensions that cause this phenomenon.

Most of the php environments we use are 32-bit, while in a 32-bit environment, a long integer is represented in 4 bytes.
That is, between-pow () and pow ()
Pow (2147483648) =
Pow (4294967296) =
This obviously cannot meet general requirements, so php has made some extensions based on the logn type. 6 bytes are used to store one integer.
That is, a positive number between-99999999999999 and 99999999999999, that is, a 14-digit integer.

In 64-bit php, this limit can be easily broken through, because in a 64-bit environment, a logn type itself is 8 bytes.

No conversion with ===

Most of the php environments we use are 32-bit, while in a 32-bit environment, a long integer is represented in 4 bytes.
That is, between-pow () and pow ()
Pow (2147483648) =
Pow (4294967296) =
This obviously cannot meet general requirements, so php has made some extensions based on the logn type. 6 bytes are used to store one integer.
That is, a positive number between-99999999999999 and 99999999999999, that is, a 14-digit integer.

In 64-bit php, this limit can be easily broken through, because in a 64-bit environment, a logn type itself is 8 bytes.
I am very grateful to xu for understanding the problem. Why didn't I think of the 64-bit and 32-bit problems before? of course, this is also related to my failure to read the PHP code and documentation.