Send sql query parameters to function

Question

TABLE wp_thesis            TABLE wp_courses

Thesis_ID Thesis_Title     Course_ID  Thesis_ID  Course 
1         thesis1          1          1          course1
2         thesis2          2          1          course2
                           3          2          course1
                           4          2          course2
                           5          2          course3

I have a select that calls the showText function onchange.

$query = "SELECT * FROM wp_thesis";
$result = mysqli_query($conn,$query);?>

<select name="ThesisTitle" onchange="showText(x,y)" required="">
  <option disabled='disabled' selected='selected' value=''></option>"; <?php
  foreach ($result as $row)
  {
      echo "<option value= {$row[Thesis_ID]}>{$row[Thesis_Title]}</option>";
  }
echo"</select><br />";?>

First thought was to send the value of the select (onchange="showText(this.value)") and then have an sql query inside showText function in order to get the two values i wanted. I read that you can't execute sql queries inside functions because Javascript is client-side, so I thought to do the sql query on php and then send the values to showText function. The query I want is this:

$query = "SELECT Course FROM wp_courses WHERE Thesis_ID={$row[Thesis_ID]} ";
$courses = mysqli_query($conn,$query);
$coursesNo = mysqli_num_rows($courses);

Tha values I want to send are $courses and $coursesNo. Is it possiple to get the value of select in the same php file, without using a button or anything like that?

Just set the courses and the course number as data-attributes of each option when you echo all the options onto the page. When the select onchange event fires, you can just select the data-attributes of the event target to get your x and y values. — Shilly
– Shilly, Commented Oct 2, 2015 at 15:25
@Shilly I tried but I don't know if I am doing it the right way. I have never used data-attributes before. — Kiki
– Kiki, Commented Oct 2, 2015 at 15:50

sandeepsure · Accepted Answer · 2015-10-02 15:34:13Z

2

Get X and Y co-ordinate before rendering option and provide it as data attribute.

    <select name="ThesisTitle" onchange="showText(this)" required="">
      <option disabled='disabled' selected='selected' value=''></option>"; <?php
      foreach ($result as $row)
      {
          echo "<option data-x={$row[Thesis_X]} data-y={$row[Thesis_Y]} value= {$row[Thesis_ID]}>{$row[Thesis_Title]}</option>";
      }
    echo"</select><br />";?>

Just after that go to showText(this) function with this as parameter and get the attribute with

  function showText(obj){
     var x_val = $(obj).attr("data-x");
     var y_val = $(obj).attr("data-y");
  }

Hope this helps to you.

answered Oct 2, 2015 at 15:34

sandeepsure

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4 Comments

Kiki Over a year ago

Foreach is taking values from table wp_thesis. The x and y values I want are not inside wp_thesis table, they are inside wp_courses.

Kiki Over a year ago

@Shilly I want the courses and coursesNo of the selected thesis. See the query at the end of my question. When someone selects a thesis title I want to get the courses that are associated with this thesis and the number of the courses. i don't know if I made myself clear.

Shilly Over a year ago

If you already include the courses associated with each thesis when you create the options, you save yourself a roundtrip to the server and hence, won't have to use anything to fetch those numbers from the database, you just check the properties of the option selected. Since both seem to be static data in this example, there's no reason to not include that data to start with.

Kiki Over a year ago

@Shilly The data are not static that's why I need to get the data from the database. I think that the only way to do it is with ajax.

Kiki · Accepted Answer · 2015-10-03 23:18:24Z

I finally found what I needed. I am posting the code.

<script language="javascript" type="text/javascript">
//Browser Support Code
function showCourses(str){
    var ajaxRequest;  // The variable that makes Ajax possible!
    try{
        // Opera 8.0+, Firefox, Safari
        ajaxRequest = new XMLHttpRequest();
    }catch (e){
        // Internet Explorer Browsers
        try{
            ajaxRequest = new ActiveXObject("Msxml2.XMLHTTP");
        }catch (e) {
            try{
                ajaxRequest = new ActiveXObject("Microsoft.XMLHTTP");
            }catch (e){
                // Something went wrong
                alert("Problem with your browser!");
                return false;
            }
        }
    }

   // Create a function that will receive data
   // sent from the server and will update
   // div section in the same page.
   ajaxRequest.onreadystatechange = function(){

        if(ajaxRequest.readyState == 4){
            var ajaxDisplay = document.getElementById('courses'); // where it should be displayed
            ajaxDisplay.innerHTML = ajaxRequest.responseText;
        }
    }

    // Now get the value and pass it to server script.
    var queryString = "?thesis_id=" + str ;
    ajaxRequest.open("GET", "http://localhost/wordpress/get_thesis/" + queryString, true);
    ajaxRequest.send(null); 
}

From the select:

<select name="ThesisTitle" id="link_block" onchange="showCourses(this.value)" required="">
    <option disabled='disabled' selected='selected' value=''></option>";<?php
    foreach ($result as $row)
    {
        echo "<option value= {$row[Thesis_ID]}>{$row[Thesis_Title]}</option>";

    }
    echo"</select><br />";?>

I am sending the Thesis_ID to http://localhost/wordpress/get_thesis/ which is a php file that does the query I needed.

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