Cast to a 32 bit integer may result in truncation PHP Propel?

问题

Looking at the source code of Propel (the PHP ORM library), I have found this method inside the propel/propel1/runtime/lib/query/Criteria.php file:

  /**
     * Set offset.
     *
     * @param int $offset An int with the value for offset.  (Note this values is
     *                    cast to a 32bit integer and may result in truncation)
     *
     * @return Criteria Modified Criteria object (for fluent API)
     */
    public function setOffset($offset)
    {
        $this->offset = (int) $offset;

        return $this;
    }

Why in the doc comments they say that the value casted to int may result in truncation??? Isn't the int kept to e.g. 4000000000 in 64 bit environment? Actually, it is, so why this "Note"?

Thanks for the attention!

回答1:

The maximum and minimum size of integer depends of the build of PHP : 32 or 64 Bits (operating system and processor must also follow)

For PHP 32-Bits the range is between ]-2147483648, 2147483647[
For PHP 64-Bits the range is between ]-9223372036854775808, 9223372036854775807[

My Test (PHP 32-Bits, WINDOWS 7 64-Bits, Intel CORE i3 64-Bits) :

<?php
$i = (int)2147483647;
var_dump($i);

Will ouput :

int(2147483647)

2nd test (just increment by 1 the last value)

<?php
    $i = (int)2147483647;
    var_dump($i);

Will ouput :

int(-2147483648)

Finally : to be sure about the max value of integer in your environment, just print this

var_dump(PHP_INT_MAX);

来源：https://stackoverflow.com/questions/27949423/cast-to-a-32-bit-integer-may-result-in-truncation-php-propel