php替换数组

<?php
$arr = [1, 2, 3, 4, 5];
$arr[2] = 10; // 替换索引为2的元素
print_r($arr);
?>

Array
(
    [0] => 1
    [1] => 2
    [2] => 10
    [3] => 4
    [4] => 5
)

<?php
$arr = ['a' => 1, 'b' => 2, 'c' => 3];
$arr['b'] = 20; // 替换键为'b'的元素
print_r($arr);
?>

Array
(
    [a] => 1
    [b] => 20
    [c] => 3
)

<?php
$arr1 = ['a' => 1, 'b' => 2, 'c' => 3];
$arr2 = ['b' => 20, 'c' => 30];
$result = array_replace($arr1, $arr2);
print_r($result);
?>

Array
(
    [a] => 1
    [b] => 20
    [c] => 30
)

<?php
$arr = ['a' => 1, 'b' => 2, 'c' => 3];
if (isset($arr['d'])) {
    $arr['d'] = 4;
} else {
    echo "Key 'd' does not exist.";
}
?>

<?php
$arr = ['a' => 1, 'b' => 2, 'c' => 3];
$arr['a'] = 'new value'; // 这里没有问题，但如果期望整数类型，就需要进行类型转换
?>