php 如何知道 Json 字符串中是否存在密钥
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how to know whether key exists in Json string
提问by Nishanth
Possible Duplicate:
How to check if an array element exists?
可能的重复：
如何检查数组元素是否存在？
apologize if i am wrong,I am new to PHP, Is there any way to find out whether key exists in Jsonstring after decoding using json_decodefunction in PHP.
抱歉，如果我错了，我是 PHP 新手，在Json使用json_decodePHP 中的函数解码后，有没有办法找出字符串中是否存在键。
$json = {"user_id":"51","password":"abc123fo"};
Brief:
简短的：
$json = {"password":"abc123fo"};
$mydata = json_decode($json,true);
user_id = $mydata['user_id'];
If json string doesn't consist of user_id,it throws an exception like Undefined index user_id,so is there any way to check whether key exists in Json string,Please help me,I am using PHP 5.3 and Codeigniter 2.1 MVCThanks in advance
如果json字符串不包含user_id，它会抛出一个异常Undefined index user_id，那么有没有办法检查Json字符串中是否存在键，请帮帮我，我正在使用PHP 5.3 and Codeigniter 2.1 MVC提前谢谢
回答by scibuff
IF you want to also check if the value is not nullyou can use isset
如果您还想检查该值是否不是null您可以使用isset
if( isset( $mydata['user_id'] ) ){
// do something
}
i.e. the difference between array_key_existsand issetis that with
即之间的差array_key_exists，并isset是与
$json = {"user_id": null}
array_key_existswill return truewhereas issetwill return false
array_key_exists会回来true而isset会回来false
回答by Jordan
You can try array_key_exists.
你可以试试array_key_exists。
It returns a boolean value, so you could search for it something like:
它返回一个布尔值，因此您可以搜索它，例如：
if(array_key_exists('user_id', $mydata)) {
//key exists, do stuff
}
