Reasons and solutions for json_encode() function errors in PHP

With the continuous development of Web applications, data interaction has become a very important link. Among them, JSON (JavaScript Object Notation) is a lightweight data exchange format that is widely used for front-end and back-end data interaction. In PHP, the json_encode() function can convert a PHP array or object into a JSON format string, and the json_decode() function can convert a JSON format string into a PHP array or object. However, sometimes you encounter errors in the json_encode() function. This article will discuss the causes and solutions to such errors.

1. Common errors of json_encode() function

1. JSON_ERROR_UTF8

This error occurs because the PHP array or object contains invalid UTF -8 characters. In PHP, UTF-8 is an encoding used to transmit and store Unicode characters on the web. However, sometimes some non-UTF-8 characters appear in the string, such as characters in encoding formats such as ISO-8859-1, and these characters will cause JSON_ERROR_UTF8 errors. For example:

$array = array(
    'name' => '张三',
    'email' => '张三@example.com',

);
$json = json_encode($array);

The above code will generate JSON_ERROR_UTF8 error.

2. JSON_ERROR_DEPTH

The reason for this error is that the level of the PHP array or object is too deep and exceeds the limit that the json_encode() function can handle. By default, the maximum number of layers that the json_encode() function can handle is 128. For example:

$array = array();
for($i = 1; $i <= 150; $i++){
    $array = array(
        'level'.$i => $array
    );
}
$json = json_encode($array);

The above code will generate JSON_ERROR_DEPTH error.

3. JSON_ERROR_RECURSION

The reason why this error occurs is that there is a circular reference in the PHP array or object. For example:

class Person{
    public $name;
    public $spouse;
}
$person1 = new Person();
$person1->name = '张三';
$person2 = new Person();
$person2->name = '李四';
$person1->spouse = $person2;
$person2->spouse = $person1;
$json = json_encode($person1);

The above code will generate JSON_ERROR_RECURSION error.

4. Other errors

In addition to the above three errors, the json_encode() function may also cause other errors, such as JSON_ERROR_CTRL_CHAR, JSON_ERROR_SYNTAX, etc.

2. Solution

There are different solutions for different errors.

1. Resolving JSON_ERROR_UTF8 error

If a PHP array or object contains non-UTF-8 characters, you can use PHP's built-in mb_convert_encoding() function to convert it to UTF- 8 format. For example:

$array = array(
    'name' => '张三',
    'email' => '张三@example.com',

);
foreach($array as &$value){
    $value = mb_convert_encoding($value, 'UTF-8', 'GBK');
}
unset($value);
$json = json_encode($array);

2. Solution to JSON_ERROR_DEPTH error

If the level of the PHP array or object is too deep, you can pass an options parameter when calling the json_encode() function to specify The maximum number of layers that can be processed. For example:

$array = array();
for($i = 1; $i <= 150; $i++){
    $array = array(
        'level'.$i => $array
    );
}
$json = json_encode($array, JSON_PARTIAL_OUTPUT_ON_ERROR | JSON_UNESCAPED_UNICODE, 512);

In the above code, the value of the options parameter is 512, that is, the maximum number of layers is 512. If this number of levels is exceeded, a JSON_ERROR_DEPTH error will be generated.

3. Solution to JSON_ERROR_RECURSION error

If a circular reference occurs in a PHP array or object, you can use the second parameter of the json_encode() function to specify a traversable object , such as Iterator. For example:

class Person{
    public $name;
    public $spouse;
    public function jsonSerialize(){
        return [
            'name' => $this->name,
            'spouse' => $this->spouse->name
        ];
    }
}
$person1 = new Person();
$person1->name = '张三';
$person2 = new Person();
$person2->name = '李四';
$person1->spouse = $person2;
$person2->spouse = $person1;
$json = json_encode(array(
    'person1' => $person1,
    'person2' => $person2
), JSON_PARTIAL_OUTPUT_ON_ERROR, 512);

In the above code, the Person class implements the jsonSerialize() method, which returns an array for the json_encode() function to serialize the object into a JSON string. When using it, when calling the json_encode() function, just pass the JSON_PARTIAL_OUTPUT_ON_ERROR constant as the second parameter.

4. Solve other errors

The solutions to other errors need to be analyzed and processed according to the specific situation.

To sum up, the json_encode() function can easily serialize PHP arrays or objects into JSON format strings, but when using it, you need to pay attention to whether the data passed is legal and perform appropriate error handling. .

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