PHP句柄json发送POST并用新的json重写现有的json

Question

I'm trying to update json file on the server on button click. So when i click the button #update I'm collecting values from input fields and insert them to json object then I sent this json object to controller.php. But how to handle this json object delete the old json file and and create new json file with the json object in it.

Lets say the json file path is : js/currencies.json

JS:

function ajaxPost(obj){
        $.ajax({
                type: "POST",
                dataType: "json",
                url: "controller.php",
                data: {myData:obj},
                contentType: "application/json; charset=utf-8",
                success: function(data){
                    alert('Items added');
                },
                error: function(e){
                    console.log(e.message);
                }
        });
    }

    $(document).ready(function(){       
                $('#update').on('click', function(){
                    var objrates = 
                    {
                        "EURbuy" : $('#eurbuy').val(),
                        "EURsell" : $('#eursell').val(),
                        "USDbuy" : $('#usdbuy').val(),
                        "USDbuy" : $('#usdbuy').val()
                    }
                    ajaxPost(objrates);
                });                                                                                                                                                                                                                         
            });

PHP :

    <?php   
    $data[] = $_POST['myData'];
    $inp = file_get_contents('js/currencies.json');
    $tempArray = json_decode($inp);
    array_push($tempArray, $data);
    $jsonData = json_encode($tempArray);
    file_put_contents('js/currencies.json', $jsonData);
?>

The php code works withouth errors but the .json file is not replaced with the new values

Answer 1

Use json_encode to return the altered object or save it to a file with file_put_contents

<?php 
    $obj = $_POST['myData'];
    $obj['key'] = 'newVal';//edith the values based on key
    echo $json = json_encode(array('newobj'=>$obj));//echo the json object if you want
     file_put_contents('js/currencies.json',$json); //replace the json with new json in the file
?>

Note: you can even pass the file name to the ajax and retrieve to to append the it alter the data:

data: {myData:obj,filename:'js/currencies.json'},

php get the url and alter the file:

$filename= $_POST['filename'];
file_put_contents($filename,$json);