SyntaxError: “JSON.parse: unexpected non-whitespac

问题:

I'm running into an issue where the JSON returned from a PHP query is not valid and I'm not really sure why; I'm still learning. When the datatype is excluded the below code returns:

{"Customer_ID":"0", "FirstName":"John", "LastName":"Smith"}
{"Customer_ID":"1", "FirstName":"Jane", "LastName":"Smith"}

otherwise it returns:

SyntaxError: "JSON.parse: unexpected non-whitespace character after ..."

I thought this might be because the record is not being returned in a single JSON response, but I can't see that being the issue as the concurrent responses are JSON. Any ideas? Any suggests? Feel free to point out the semantic issues.

HTML:

getRecord("*", "customer", "");

JavaScript:

function getRecord(field, table, condition) {
    var request = $.ajax({
        url: "./handler.php",
        method: "GET",
        dataType: "JSON",
        cache: "false",
        data: {
            action: "SELECT",
            field: `${field}`,
            table: `${table}`,
            condition: `${condition}`,
        },
    });

    request.done(function(data, status, xhr) {
        console.log(data, status, xhr);
    });

    request.fail(function(xhr, status, error) {
        console.log(xhr, status, error);
    });

};

PHP:

<?php

    # IMPORT SETTINGS.
    include "settings.php";

    # FUNCTION DISPATCHER.
    switch($_REQUEST["action"]) {

        case "SELECT":
            getRecord($conn);
            break;

        default:
            printf('Connection Error: Access Denied.');
            mysqli_close($conn);
    }

    # LIST OF COLUMNS THAT WE NEED.

    function getRecord($conn) {
        $table = $_REQUEST["table"];
        $field = $_REQUEST["field"];
        $condition = $_REQUEST["condition"];

        if (!empty($condition)) {
            $query = "SELECT $field FROM $table WHERE $condition";
        } else {
            $query = "SELECT $field FROM $table";
        }

        if ($result = mysqli_query($conn, $query)) {
            while ($record = mysqli_fetch_assoc($result)) {
                echo json_encode($record);
            }
        }

        # CLOSE THE CONNECTION.
        mysqli_close($conn);

    }

?>

回答1:

Your JSON is not valid because it consists of multiple objects. What you need to do is put all your results into an array and then echo the json_encode of that. Try something like this:

    $records = array();
    if ($result = mysqli_query($conn, $query)) {
        while ($records[] = mysqli_fetch_assoc($result)) {
        }
    }
    echo json_encode($records);

This will give you an output that looks something like this:

[
    {"Customer_ID":"0", "FirstName":"John", "LastName":"Smith"},
    {"Customer_ID":"1", "FirstName":"Jane", "LastName":"Smith"}
]

and you can access each of the elements in your Javascript by something like

let customer = data[0].FirstName + ' ' + data[0].LastName;