如何进行php动态查询

Question

im trying to change query depending on what user has selected. In my case there are displayed two photos with labels pulled from data base. And depending which image is clicked i want that label to be used in query who will display items associated in database with that label. I tried using global variables, but it i didn't work for me. I cant figure out how to insert data into query after user clicked something

There is code fragment where i pull photos with labels from database, and depending on which i select i want "$modeliai_results['Modelis']" (vehicle model label) to be sent and used in another query below

<div class="eile">
    <?php
    echo '
    <a href="standartiniskatalogas.php?page=kategorijos"/>
    <img src="data:image/jpeg;base64,'.base64_encode( $modeliai_results['Nuotrauka'] ).'"/>
    <div class="description">'.$modeliai_results['Marke'].' '.$modeliai_results['Modelis'].'
    </div></a>';
?>

Page from second image which should execute query depending on selection from previous page:

<?php
    $kategorijos_sql="SELECT * FROM kategorijos (HERE SHOULD BE ADDED: "WHERE Modelis='MODEL NAME WHICH WAS SELECTED WHEN PRESSED ON IMAGE'";
    $kategorijos_query=mysqli_query($dbconnect, $kategorijos_sql);
    $kategorijos_results=mysqli_fetch_assoc($kategorijos_query);

do{
    echo '
    <div class="eile2">
    <a href="isore/isore.html">
    <img src="data:image/jpeg;base64,'.base64_encode( $kategorijos_results['Nuotrauka'] ).'"/>
    <div class="description">'.$kategorijos_results['Kategorija'].'</div>
    </a></div>'; /* uzdaro echo*/
    }
    while ($kategorijos_results=mysqli_fetch_assoc($kategorijos_query))
     ?>

ps. Im not using any extra tools or libraries.

Selecting object Display data associated with object

Answer 1

My mistake was that i concentrated on "onclick" event which would set global variable and that global variable would be used in query. Problem was that, php with java script not so big friends and would create not linkable URLs to same content. The solution was to use simple thing "$_GET". Assign $_GET to some php variable, and then use it in "href". That way when you click on any kind of object with "a href="'.$variable.'"> bla bla /a>" you get redirected to page with added tail to URL from which you can access to use in other queries

 <?php
        $model= $_GET['model']; //variable from URL tail  
        $category= $_GET['category'];

        $category_sql="SELECT * FROM service WHERE Model='$model' AND Category='$category'"; //my SQL where i use variables selected from URL
        $category_query=mysqli_query($dbconnect, $category_sql);
        $category_results=mysqli_fetch_assoc($category_query);
        do{

            echo ' //print html together with php code
        <tr class="data">
            <td>
                <a href="catalogue.php? page=service&model='.$model.'&category='.$category.'&service='.$category_results['Name'].'"> //here i make href which when clicked will pass values named with $ sign
<img src="data:image/jpeg;base64,'.base64_encode( $category_results['Image'] ).'"/>//Here i take image from data base
<br><button>'.$category_results['Name'].'</button></a>
            </td>
            <td> <p>'.$category_results['Description'].'</p> //I take values from data base
            </td> 
            <td>'.$category_results['Price'].' &euro;</td>
        </tr>';
    }
    while ($category_results=mysqli_fetch_assoc($category_query)) //loop which cycles through all data base items
         ?>