php 关联数组追加

<?php
// 初始化一个关联数组
$student = array(
    "name" => "Alice",
    "age" => 20,
    "major" => "Computer Science"
);

// 追加一个新的键值对
$student["grade"] = "A";

// 输出结果
print_r($student);
?>

<?php
$student = array(
    "name" => "Alice",
    "age" => 20,
    "major" => "Computer Science"
);

// 检查键名是否已存在
if (!isset($student["grade"])) {
    $student["grade"] = "A";
} else {
    echo "Key 'grade' already exists.";
}

// 或者使用 array_merge
$new_student = array("grade" => "A");
$student = array_merge($student, $new_student);

print_r($student);
?>