PHP code for verification of limit on number of array elements. (PHPの配列要素数の上限を検証するコード)

verifyLimitOfArrayElements.php

<?php

/**
 * Code for verification of limit on number of array elements
 */

 // initialization
$a = [];

// lower limit of array index
// - lower limit of integer:
//   - 32bit-system: - (2 ** 31) === -2147483648
//   - 64bit-system: - (2 ** 63) === -9223372036854775808
$a[PHP_INT_MIN] = 'foo';
var_dump($a);

// under limit
// value of $i is to be treated as a float value
// - 64bit-system: float(-9.223372036854776E+18)
$i = PHP_INT_MIN - 1;
var_dump($i);

// this results in overwriting the element of the lowest index,
// because the value of $i is rounded to PHP_INT_MIN.
$a[$i] = 'bar';
var_dump($a);

// upper limit of array index
// - upper limit of integer:
//   - 32bit-system: 2 ** 31 - 1 === 2147483647
//   - 64bit-system: 2 ** 63 - 1 === 9223372036854775807
$a[PHP_INT_MAX] = 'baz';
var_dump($a);

// over limit
// >> results in "PHP Fatal error"
$a[] = 'qux';
var_dump($a);

This code results in:

• on 64bit-system:

~/work/phptest$ php -f verifyLimitOfArrayElemets.php 
array(1) {
  [-9223372036854775808]=>
  string(3) "foo"
}
float(-9.223372036854776E+18)
array(1) {
  [-9223372036854775808]=>
  string(3) "bar"
}
array(2) {
  [-9223372036854775808]=>
  string(3) "bar"
  [9223372036854775807]=>
  string(3) "baz"
}
PHP Fatal error:  Uncaught Error: Cannot add element to the array as the next element is already occupied in /home/macocci7/work/phptest/verifyLimitOfArrayElemets.php:37
Stack trace:
#0 {main}
  thrown in /home/macocci7/work/phptest/verifyLimitOfArrayElemets.php on line 37