今天看见一张 php 面试图片(一)

$fruits = [
    'apple' => 'red',
    'banana' => 'yellow',
    'orange' => null
];
array_key_exists("apple", $fruits);       
array_key_exists("banana", $fruits);      
array_key_exists("orange", $fruits);      // true

array_key_exists("orange", $fruits);      // true

$fruits = [
    'apple' => 'red',
    'banana' => 'yellow',
    'orange' => null
];
isset($fruits["apple"]);      
isset($fruits["banana"]);     
isset($fruits["orange"]);     // false

isset($fruits["orange"]);     // false