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Editorial Team
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Asked: 2026-06-12T20:14:44+00:00

I am trying to draw on a html canvas using values from a php

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I am trying to draw on a html canvas using values from a php table. From my testing the php is reading values from the table correctly and is also calling the javascript function, but its not working to draw a series of 20*20 rectangles with a different x value.

<html>
    <script type="text/javascript">
    function draw( i ) {

    alert(i);


    var canvas = document.getElementById('mycanvas');
    var drawshape = canvas.getContext('2d');
    canvas.width = 800;
    canvas.height = 400;
    drawshape.fillStyle = '#00ff00';
    drawshape.fillRect(50 * i , 50, 20, 20);
  }


</script>
    <body>
        <canvas id="mycanvas"></canvas>
    </body>
</html>


<?php


    $query4 = 'SELECT * FROM graph_table';
    $result4 = mysql_query($query4);

    while($person4 = mysql_fetch_array($result4)) {
        $indent =  $person4['indent'];
        echo '<script type="text/javascript">    draw( <?php echo $indent; ?> );         </script>';
    }

?>
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1 Answer

  1. Editorial Team

    change your draw function

    and add a parameter everytime the result from db is generated

    ex

    <html>
<script type="text/javascript">
        function draw(indent) {
        var canvas = document.getElementById('mycanvas');
        var drawshape = canvas.getContext('2d');
        canvas.width = 800;
        canvas.height = 400;

        drawshape.fillStyle = #00ff00;
        drawshape.fillRect(50 *indent , 50, 20, 20);
    }
</script>
</html>


<?php
$query = 'SELECT * FROM table';
$result = mysql_query($query);
    while($value = mysql_fetch_array($result)) {
        $indent =  $value['indent'];
        echo '<script type="text/javascript">    draw('.$indent.');      </script>';
    }
?>
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