PHP / MySQL：SyntaxError：JSON.parse：JSON数据第1行第1列的意外字符

Question

I have this MySQL table:

mysql> select * from  members;
+-------+-----------+-----------+
| memid | firstname | lastname  |
+-------+-----------+-----------+
|     1 | billal    | begueradj |
|     2 | bill      | gates     |
|     3 | steve     | jobs      |
+-------+-----------+-----------+
3 rows in set (0.00 sec)

I have this code:

<?php
$output = array('error' => false);
$members = array();

try {
    $db = new PDO('mysql:host=localhost;dbname=bill;charset=utf8',
                   'root',
                   ''
    );
} catch(Exception $e) {
    die('Error in connecting to DB: <br/>'.$e->getMessage());
}

$response = $db->query('SELECT * FROM members');
while($row = $response->fetch()){
    echo $row['firstname'].' ';
    echo $row['lastname'].'<br/>';
    array_push($members, $row);
}

$output['members'] = $members;
$response->closeCursor();
$json = json_encode($out);
echo $json; // outputs correctly
header("Content-type: application/json");    // error here
die();
?>

And I am getting this error message when I run the PHP file containing the PHP code above:

SyntaxError: JSON.parse: unexpected character at line 1 column 1 of the JSON data

Why this happens?

P.S. Of course, when I comment this line: //header("Content-type: application/json"); the error message disappears

EDIT: New code version following the comments below:

<?php
    header("Content-type: application/json");
    $output = array('error' => false);
    $members = array();

    try {
        $db = new PDO('mysql:host=localhost;dbname=bill;charset=utf8',
                       'root',
                       ''
        );
    } catch(Exception $e) {
        die('Error in connecting to DB: <br/>'.$e->getMessage());
    }

    $response = $db->query('SELECT * FROM members');
    while($row = $response->fetch()){       
        array_push($members, $row);
    }

    $output['members'] = $members;
    $response->closeCursor();
    $json = json_encode($out); 
    //echo $json;    

?>

Still getting the same error message

Answer 1

header() should be placed above all output, so before you echo anything.

Plus, since your not encoding the whole thing to JSON, instead only parts, I'm guessing your missing start and end of the JSON.

Correct JSON outputs:

ex1:

{
  "key1": "value1",
  "key2": "value2",
  "key3": "value3"
}

ex2:

[
  {
    "key1": "value1",
    "key2": "value2",
    "key3": "value3"
  },
  {
    "key1": "value1",
    "key2": "value2",
    "key3": "value3"
  },
  {
    "key1": "value1",
    "key2": "value2",
    "key3": "value3"
  }
]

PHP:

<?php

$output = ["error" => false, "members" => []];

try {
  $db = new PDO("mysql:host=localhost;dbname=bill;charset=utf8", "root", "");
} catch(Exception $e) {
  die("Error in connecting to DB: <br/>{$e->getMessage()}");
}

$response = $db->query("SELECT * FROM members");

while($row = $response->fetch(PDO::FETCH_ASSOC)) {
  array_push($output["members"], $row);
}

$response->closeCursor();

$json = json_encode($output);

header("Content-type: application/json");

echo $json;