Use PHP to determine whether a JSON object exists

This article mainly introduces the relevant information on the method (recommended) of PHP to determine whether a JSON object exists. It is very good and has reference value. Friends in need can refer to it

Read in php during the actual test When taking a json array, using a simple if or array_key_exists to determine whether the object exists will result in an error. The following is the correct judgment method found on Google

In fact, an error occurs because I am not very proficient in PHP. Maybe the correct judgment method I think is not the most perfect solution or even wrong. This blog post is reserved for your own use

Error code:

$structure = imap_fetchstructure($connection, $id, FT_UID);
if (array_key_exists('parts', $structure))
{
}

There will be an error Warning: array_key_exists() expects parameter 2 to be array, boolean given

The correct solution is:

if (is_array($structure) && array_key_exists('parts', $structure)) { //...magic stuff here }

And there is another way to use isset to directly judge:

if(isset($structure['parts']))
{
} 
　　//这个函数用来测试变量是否已经配置。若变量已存在则返回 true 值。其它情形返回 false 值。
　　//因此需要若变量存在且值不为NULL，才返回 TURE

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