How to fetch data from a database using PHP and pass it to Javascript

Question

I am making a website using HTML, CSS, MySQL and Javascript that will allow the user to login and play a quiz, the quiz has 40 questions.

The Javascript code bellow is a countdown timer, that contains the variable named "questions" after 40 seconds, it will pass automatically to the next question.

    var i = 0;
var cEl = document.getElementById('countdown');
var qEl = document.getElementById('question');
var questions = [
 
  'Question1 ?',
  'Question2 ?',
  'Question3 ?',
  'Question4 ?'
];

var Countdown = function (time) {
  this.time = time;
  this.observers = [];
};

Countdown.prototype.start = function () {
  setTimeout(function () {
    if (this.time-- > 0) {
      this.updateObservers();
      this.start();
    }
  }.bind(this), 1000);
};

Countdown.prototype.addObserver = function (observer) {
  this.observers.push(observer);
};

Countdown.prototype.updateObservers = function () {
  var i, l = this.observers.length;
  for (i = 0; i < l; i++) {
    this.observers[i](this.time);
  }
};

function printTime (time) {
  cEl.innerHTML = time + 's';
}

function nextQuestion (time) {
  if (time <= 0) run();
}

function run () {
  var c;
  if (i < questions.length) {
    qEl.innerHTML = questions[i++];
    c = new Countdown(40);
    c.addObserver(printTime);
    c.addObserver(nextQuestion);
    printTime(c.time);
    c.start();
  } else {
    document.body.innerHTML = 'Fin du quiz';
  }
}

run();

And this is the part of my "quiz.php" file where I want the questions to be inserted :

<!doctype html>
<html>

<head>
  <title>
    Quiz
  </title>
</head>

<body class="no-scroll">
  <div>
    <!-- some code here -->
  </div>
  <!-- some code here -->

  <script src="js/countdown_script.js"></script>
</body>

</html>

For now, the questions are in the following variable :

var questions = [
     
      'Question1 ?',
      'Question2 ?',
      'Question3 ?',
      'Question4 ?'
    ];

But I want to use questions and their answers that are already in a database, each question has 2 or 3 possible answers, I've read that I'm not supposed to add the php code inside of a .js file, I tried to add the questions variable in the php code bellow but it did not work :

<!doctype html>
<html>

<head>
  <title>
    Quiz
  </title>
</head>

<body class="no-scroll">
  <div>
    <!-- some code here -->
  </div>
  <!-- some code here -->

  <script src="js/countdown_script.js"> 
 var questions = [  
  'Question1 ?',
  'Question2 ?',
  'Question3 ?',
  'Question4 ?'
];</script>
</body>

</html>

What is the best way to do that in my case? Given that I'm still a beginner and I only know html, css, some javascript, php and mysql.

Nice question though a bit broad. good luck. Please mark with green check mark an accepted answer when you find one. — Drew
– Drew, Commented Jan 12, 2016 at 20:55

Adam · Accepted Answer · 2016-01-10 21:30:48Z

You need to make a small API.

Step 1. make an additional page in your application that will output clean JSON array with data from the dataabse

For example: myApiWithQuestions.php

{
questions: {
    question1: {
        "content":"content of the question",
        "possibleAnswers":[
             "something", "another answer"
         ] 
    },
    question2: {
        "content":"content of the question",
        "possibleAnswers":[
             "something", "another answer"
         ] 
    },

}}

Step 2: Make an ajax call using JQuery to look for the page you have just created

$(document).ready(){
    $.ajax({
        url: "myApiWithQuestions.php",
    })
    .done(function( data ) {

        //use data as an array, iterate through it and put your questions to the DOM

    });
}

On .done function continue with execution of your script

bluedenham · Accepted Answer · 2016-01-10 19:53:34Z

-2

Where did you read that you're not supposed to run PHP code in Javascript?

Anyway, it doesn't really matter: you can. I do it all the time.

    <script type="text/javascript" src="js/countdown_script.js"> 
    <script type="text/javascript"><!--
    var questions = [  
    <?php
    //create and run your mysql query

    //loop through your results
    while($row=mysql_fetch_array($results)){
      //print your results in javascript format
      printf("'%s ?'\n",$row['question']);
    }
    ?>
    ];
    --></script>

answered Jan 10, 2016 at 19:53

bluedenham

291 silver badge7 bronze badges

7 Comments

Ouissal Over a year ago

I meant I've read that I'm not supposed to run PHP inside of a .js file. I've tried to do it this way but it didn't work.

Rasclatt Over a year ago

You can't do it on a .js but you can on a php page

user2399035 Over a year ago

It's not a good practice! Better to run the php outside, turn the resulting array to Json and use it in js

bluedenham Over a year ago

Correct, you cannot run PHP inside of a JS file, however the example I'm showing was running this on your PHP page, within the constraints of the JS tags. Since that is what the OP asked, that's what was delivered. Of course there are many, many other ways and methods of accomplishing this task, but this is the most time efficient.

Ouissal Over a year ago

@bluedenham I've tested it but it didn't work, it prints nothing, I don't know why

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