Add Grid Lines to a PHP GD Line Graph

SQL concepts used: SELECT · ORDER BY

<?php
$image = imagecreatetruecolor(600, 360);
$background = imagecolorallocate($image, 255, 255, 255);
$grid = imagecolorallocate($image, 220, 220, 220);
imagefilledrectangle($image, 0, 0, 599, 359, $background);

for ($x = 50; $x <= 550; $x += 50) {
    imageline($image, $x, 30, $x, 320, $grid);
}
for ($y = 70; $y <= 320; $y += 50) {
    imageline($image, 50, $y, 550, $y, $grid);
}
?>

imageline ($im,$x2, $y_max,$x2,$y2,$grid_color);

<?php
require "config.php"; // provides $pdo

$stmt=$pdo->query('SELECT month, sales FROM gd_graph ORDER BY id');
$points=$stmt->fetchAll(PDO::FETCH_ASSOC);

$x_gap=40; // The gap between each point in y axis 

$x_max=$x_gap*13; // Maximum width of the graph or horizontal axis
$y_max=160; // Maximum hight of the graph or vertical axis
// Above two variables will be used to create a canvas of the image//

$im = imagecreatetruecolor($x_max, $y_max);
$background_color = ImageColorAllocate ($im, 234, 234, 234);
$text_color = ImageColorAllocate ($im, 233, 14, 91);
$graph_color = ImageColorAllocate ($im,25,25,25);

$grid_color = ImageColorAllocate ($im,125,125,125);

$x1=0;
$y1=0;
$first_one="yes";
foreach($points as $nt){
//echo "$nt[month], $nt[sales]";
$x2=$x1+$x_gap; // Shifting in X axis
$y2=$y_max-$nt['sales']; // Coordinate of Y axis
ImageString($im,2,$x2,$y2,$nt['month'],$graph_color);

// Drawing the grid vertically//
imageline ($im,$x2, $y_max,$x2,$y2,$grid_color); 

//Line above is to print month names on the graph
if($first_one=="no"){ // this is to prevent from starting $x1= and $y1=0
imageline ($im,$x1, $y1,$x2,$y2,$text_color); // Drawing the line between two points//
}
$x1=$x2; // Storing the value for next draw
$y1=$y2;
$first_one="no"; // Now flag is set to allow the drawing
}
//header ("Content-Type: image/jpeg");

ImageJPEG ($im);
?>

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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