PHP GET接口测试报错：JSON解析异常及unexpected ''问题排查

First, let's fix the obvious syntax error in your code snippet. The line $this->connection = ... is incomplete—you need to finish assigning the database connection here. For example, if your DB_connection class has a method like getConnection(), it should look like:

function __construct(){
    $this->db = new DB_connection();
    $this->connection = $this->db->getConnection(); // Complete this line!
}

An incomplete line like that will throw the unexpected '' syntax error you're seeing.

Next, let's tackle the JSON parse error. Here are the most common fixes:

1. Ensure No Extra Output Before JSON Header #

Any whitespace, error messages, or echo statements before header('Content-Type: application/json'); will break the JSON response. Make sure:

• There's no whitespace before the opening <?php tag in your script or connection.php.
• Disable PHP error output temporarily while testing (or catch errors properly) so they don't leak into the JSON response. Add these lines at the top of your script:

  error_reporting(0);
  ini_set('display_errors', 0);
  

2. Validate Your JSON Output #

After processing the GET variables, make sure you're only outputting valid JSON using json_encode(). For example:

// Process your GET variables
$var1 = $_GET['var1'];
$var2 = $_GET['var2'];
$var3 = $_GET['var3'];

// Do your database operations here...

// Prepare your response data
$response = array(
    'status' => 'success',
    'data' => $your_data
);

// Encode and output the JSON
echo json_encode($response);
exit; // Make sure nothing else is output after this

3. Check for Database Connection Errors #

If your DB_connection class throws errors or outputs messages, that will corrupt the JSON. Make sure it handles connection errors silently (or logs them instead of echoing) so they don't interfere with the response.

4. Test with Postman Correctly #

In Postman, make sure you're sending a GET request with the 3 variables as query parameters (not in the body). Also, check the "Body" tab in Postman to see what actual response your script is returning—if it's showing PHP error messages, that's the root cause of the JSON parse error.

If you still have issues, share the complete code of your script and connection.php so we can spot other potential issues!

内容的提问来源于stack exchange，提问作者Muhammad Hamza