Detailed introduction to long integer forced conversion overflow in PHP 32-bit system

CleverCode recently encountered a PHP project plastic conversion problem. mysqlThere is a field id that is bigint and contains a long integer, such as id = 5147486396. However, the php code is deployed on multiple machines due to historical reasons, among which machine A is a 32-bit system and machine B is a 64-bit system. The problem now is that the page access is normal in the 64-bit system. Access error in 32-bit system. The reason is php shaping overflow.

1 A machine demonstration

1.1 Get the system bit number of A machine

# getconf LONG_BIT

1.2 Shaping conversion code

<?php

$id = 5147486396;
echo &#39;$id：&#39;.$id."\r\n";

$value = (int)$id;
echo &#39;(int)$id：&#39;.$value."\r\n";

$value = intval($id);
echo &#39;intval($id)：&#39;.$value."\r\n";

$value = filter_var($id, FILTER_VALIDATE_INT);
echo &#39;filter_var($id, FILTER_VALIDATE_INT)：&#39;."\r\n";
var_dump($value);


?>

1.3 Running results

(int)5147486396的结果是852519100，intval(5147486396)的结果是852519100，filter_var(5147486396, FILTER_VALIDATE_INT)结果是false。

2 Machine B demonstration

2.1 Get the number of system digits of B machine

# getconf LONG_BIT

2.2 Plastic conversion code

<?php

$id = 5147486396;
echo &#39;$id：&#39;.$id."\r\n";

$value = (int)$id;
echo &#39;(int)$id：&#39;.$value."\r\n";

$value = intval($id);
echo &#39;intval($id)：&#39;.$value."\r\n";

$value = filter_var($id, FILTER_VALIDATE_INT);
echo &#39;filter_var($id, FILTER_VALIDATE_INT)：&#39;."\r\n";
var_dump($value);


?>

2.3 Running result

(int)5147486396的结果是5147486396，intval(5147486396)的结果是5147486396，filter_var(5147486396, FILTER_VALIDATE_INT)结果是5147486396。

3 Conclusion

The word length of integers is platform-dependent, although the usual maximum is about two billion (32-bit signed). The maximum value on 64-bit platforms is usually around 9E18. PHP does not support unsigned integers. Integer The word length of the value can be represented by the constant PHP_INT_SIZE. Since PHP 4.4.0 and PHP 5.0.5, the maximum value can be represented by the constant PHP_INT_MAX

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