How to store and get image from a image variable (SESSION)? - php

Question

here is my code, test1.php works, test2.php not works.
test1.php:
<?php
session_start();
header('Content-type: image/jpeg');
$text = rand(1000,9999);
$font_size = 5;
$image_width = imagefontwidth($font_size) * strlen($text);
$image_height = imagefontheight($font_size);
$image = imagecreate($image_width, $image_height);
imagecolorallocate($image, 255, 255, 255);
$text_color = imagecolorallocate($image, 0, 0, 0);
imagestring($image, $font_size, 0, 0, $text, $text_color);
$_SESSION['image'] = $image;
$image_session = $_SESSION['image'];
imagejpeg($image_session);
?>
test2.php:
<?php
session_start();
header('Content-type: image/jpeg');
$image_session = $_SESSION['image'];
imagejpeg($image_session);
?>
As you can see, test1.php create a random image.
I can use:
<img src="test1.php">
to show the image from test1.php in any pages.
but, I want to use if else statement in other php files.
for example:
if users click submit button and enter nothing(no answer), the image will still the same, they have to answer the same question. if failed, the image will change.
I don't want to use javascript to prevent users input nothing and store images in disk.
so, I think that I need a variable to store the image that can be used again.
but I found I cannot use above method.
how can I achieve this?

Answer 1

imagecreate() returns a resource representing given image. PHP's sessions cannot store resource-type variables (more precisely - PHP is unable to serialize them upon script end), see http://php.net/manual/en/function.session-register.php:
Note: It is currently impossible to register resource variables in a
session. ...
You may serialize the image to a string and store this string to the session (not tested):
test1.php:
...
ob_start();
imagejpeg($image);
$contents = ob_get_contents();
ob_end_clean();
$_SESSION['image'] = $contents;
test2.php:
header('Content-type: image/jpeg');
die($_SESSION['image']);

Answer 2

Without knowing much about the context, can't you do something like
session_start();
$_SESSION['randomValue'] = mt_rand(1000,9999);
if(someValueIsEntered){
$_SESSION['randomValue'] = mt_rand(1000,9999);
}
echo "<img src='test.php?random=".$_SESSION['randomValue']."'/>";
Test.php
$randomValue = filter_input(INPUT_GET, 'random');
header('Content-type: image/jpeg');
$text = $randomValue;
$font_size = 5;
$image_width = imagefontwidth($font_size) * strlen($text);
$image_height = imagefontheight($font_size);
$image = imagecreate($image_width, $image_height);
imagecolorallocate($image, 255, 255, 255);
$text_color = imagecolorallocate($image, 0, 0, 0);
imagestring($image, $font_size, 0, 0, $text, $text_color);
imagejpeg($image);
Multiple parameters example:
Store the information about the image in an array.
session_start();
if(!isset($_SESSION['imageData']){
$_SESSION['imageData'] = array(
"random" => mt_rand(1000,9999),
"x1" => mt_rand(0,10),
"x2" => mt_rand(0,10)
);
}
if(someValueIsEntered){
//Randomize array again.
}
$imageString = "test.php";
foreach ($_SESSION['imageData'] as $key => $value) {
$index = current($array);
if($index == 0) {
$seperator = "?";
} else {
$seperator = "&";
}
$imageString .= $seperator.$key."=".$value;
}
echo "<img src='".$imageString."'/>";
And just call them in the test.php then.