Call PHP function with JavaScript Ajax to get database values

Question

i try to call a php function with Ajax. This is my JavaScript code in my html file:

<script type="text/javascript">
    function ajax(){
        $.ajax({
            type:"POST",
            url: "SQLCommunication.php",
            dataType: "JSON",
            success : function(json){
                json = jQuery.parseJSON(json);
                alert(json.value);
            }
        }
        )
    }

    $("#btn_refresh").click(function(){
       ajax(); 
    });
</script>

I don't know if i have to specify which PHP function i actually want to call? I also don't know how i do that.

My PHP function:

header('Content-Type: application/json');
function readValue(){
    $conn = establishConnection();
    if($conn->connect_error){
        die("Connection failed: " . $conn->connect_error);
    }

    $sql = "SELECT datetime, value FROM tempvalues";
    $result = $conn->query($sql);

    if($result->num_rows > 0){
        $row = $result->fetch_assoc();
        $arr["datetime"] = $row["datetime"]; //return datetime and value as array
        $arr["value"] = $row["value"];
        if(is_ajax()){
            return json_encode($arr);
        } else {
            return $arr;
        }
    }

    $conn->close();
}

So the problem is now, that nothing happens if i press the button.

You need to invoke the readValue() function in your PHP code and echo its result. — Rory McCrossan
– Rory McCrossan, Commented Mar 31, 2016 at 20:49
Also make sure you hit that readValue function in your controller. — Mateen Kajabadi
– Mateen Kajabadi, Commented Mar 31, 2016 at 20:50

Chay22 · Accepted Answer · 2016-03-31 21:44:24Z

1

I'll rewrite to my style

jQuery

<script type="text/javascript">
    $("#btn_refresh").click(function(){
        $.ajax({
            type:"POST",
            url: "SQLCommunication.php",
            dataType: "JSON",
            success : function(data){
                console.log(data);
                if(data.status === "success"){
                    alert("success");
                }else{
                    alert("error");
                }
            }
            error : function(XHR, status){
                 alert("fatal error");
            }
        })
    });
</script>

PHP

header('Content-Type: application/json');
function readValue(){
    $conn = establishConnection();
    if($conn->connect_error){
        die("Connection failed: " . $conn->connect_error);
    }

    $sql = "SELECT datetime, value FROM tempvalues";
    $result = $conn->query($sql);

    if($result->num_rows > 0){
        $row = $result->fetch_assoc();
        $arr["datetime"] = $row["datetime"]; //return datetime and value as array
        $arr["value"] = $row["value"];
        $arr["status"] = "success";
    }else{
        $arr["status"] = "error";
    }

    return json_encode($arr);
    $conn->close();
}

echo readValue();

Untested

Updated

functions.php

function readValue(){
    $conn = establishConnection();
    if($conn->connect_error){
        die("Connection failed: " . $conn->connect_error);
    }

    $sql = "SELECT datetime, value FROM tempvalues";
    $result = $conn->query($sql);

    if($result->num_rows > 0){
        $row = $result->fetch_assoc();
        $arr["datetime"] = $row["datetime"]; //return datetime and value as array
        $arr["value"] = $row["value"];
        $arr["status"] = "success";
    }else{
        $arr["status"] = "error";
    }

    return json_encode($arr);
    $conn->close();
}

function writeValue(){
     ...
}

SQLCommunication.php

header('Content-Type: application/json');
if(!isset($_GET['func']) && empty($_GET['func'])){
   //make the file inaccessible without $_GET
   $arr['status'] = "error";
   echo json_encode($arr);
   exit();
)

if($_GET['func'] === "readvalue"){
   echo readValue();
}elseif($_GET['func'] === "writevalue"){
   echo writeValue();
}elseif($_GET['func'] === "whatever"){
   //whatever...
}

  ....

jQuery

$("#btn_refresh").click(function(){
    $.ajax({
        type:"POST",
        url: "SQLCommunication.php?func=readvalue", //SQLCommunication.php?func=writevalue
        dataType: "JSON",
        success : function(data){
            console.log(data);
            if(data.status === "success"){
                alert("success");
            }else{
                alert("error");
            }
        }
        error : function(XHR, status){
             alert("fatal error");
        }
    })
});

edited Mar 31, 2016 at 21:44

answered Mar 31, 2016 at 21:04

Chay22

2,9042 gold badges19 silver badges25 bronze badges

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5 Comments

binaryBigInt Over a year ago

thanks, that works. So i can't indicate which function of the .php - file i want to use? The ajax thing just gives me the echo of the php file. So basically, if i want to call more php functions i have to make a new file for every one?

Chay22 Over a year ago

@binaryBigInt That's a broad question, well, for me. For the code up there? You can save the functions like readValue() up there in functions.php, you name it. Access the functions.php through SQLCommunication.php. Then, use $_GET method on SQLCommunication.php. That's how to make it dynamic, at least what's on my mind right now. I can update my answer if you want it.

binaryBigInt Over a year ago

Yes, please give me a short example of what you mean. That would be very helpfull!

binaryBigInt Over a year ago

Thanks for your updated post but now i am getting an error: pastebin.com/01jXS1XG

Chay22 Over a year ago

@binaryBigInt What kind of error? Post on another question, please.

Kevin Grosgojat · Accepted Answer · 2016-03-31 20:48:53Z

1

If you want to see the result in your ajax response, you have to use echo(), or any other printing method in your controller instead of return

answered Mar 31, 2016 at 20:48

Kevin Grosgojat

1,3799 silver badges13 bronze badges

2 Comments

binaryBigInt Over a year ago

What do you mean with "controller"?

Kevin Grosgojat Over a year ago

Script or function if you prefer. Controllers are code file's name in MVC architecture (like Symfony or Laravel for PHP).

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