The solution to the problem of not getting the key value when converting json to array php

When we use PHP to convert from JSON serialized string to array, we sometimes encounter some problems. One of the most common problems is missing keys in the converted array.

For example, we use the following code to get data from a JSON string:

$json_str = '{"name":"John","age":30,"city":"New York"}';
$data = json_decode($json_str, true);

This code is actually very simple, it is to convert a JSON string into an associative array. However, sometimes the converted array does not have the correct key values. This may be caused by the JSON string containing some invisible characters or irregular structure.

The following introduces some problems that may cause key values ​​to be missing after conversion, and gives corresponding solutions.

Problem 1: The JSON string contains invisible characters

Sometimes, the JSON string contains some invisible characters, such as spaces or newlines. These characters may appear harmless, but can cause the JSON parser to fail to parse correctly. This will cause the conversion from JSON string to array to fail.

Solution:

You can try to use PHP's trim() function to remove invisible characters from the string. For example:

// 移除 JSON 字符串中的不可见字符
$json_str = trim($json_str);

// 将 JSON 字符串转换为关联数组
$data = json_decode($json_str, true);

Issue 2: Key names in JSON strings do not conform to PHP variable name specifications

Key names in JSON can contain a variety of characters, not just letters and numbers. However, in PHP, variable names must follow certain naming conventions. If a key name in JSON does not conform to these specifications, the JSON parser will not parse the key name correctly and the conversion from JSON string to array will fail.

Workaround:

If you have no control over the incoming JSON string, you can try setting PHP's associative array option to false. This will cause the JSON parser to parse objects in JSON as standard objects instead of associative arrays. For example:

// 将 JSON 字符串转换为标准对象
$data = json_decode($json_str, false);

Problem 3: Key names in the JSON string are duplicated with other key names

Key names in JSON must be unique. If two or more keys in a JSON string have the same name, the parser will not be able to distinguish between them. This will cause the conversion from JSON string to array to fail.

Workaround:

If you are unable to modify the incoming JSON string, try setting PHP's JSON_BIGINT_AS_STRING option to true. This will force the JSON parser to parse all numbers in JSON as strings. For example:

// 将 JSON 字符串中的数字解析为字符串
$data = json_decode($json_str, true, 512, JSON_BIGINT_AS_STRING);

Problem 4: JSON contains illegal structures

The JSON format has its limitations and constraints. If a JSON string does not comply with these limits and constraints, the parser will not be able to parse the string correctly and the conversion from JSON string to array will fail.

Workaround:

If you have no control over the incoming JSON string, you need to ensure that it conforms to the JSON specification. Otherwise, you need to fix the error in the JSON string.

Finally, here are some additional workarounds:

• Make sure the JSON string is a valid UTF-8 string.
• If you are using PHP version lower than 5.4, you need to install the JSON extension.
• Try using PHP's stripslashes() function before passing in the json_decode() function.

Summary:

When a JSON string cannot be converted from JSON to an array correctly, you can think of many solutions. Either way, you need to understand the characteristics and limitations of JSON to be able to identify and fix errors that may occur. Let's work together to solve these problems as soon as possible!

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