how to clear cache using PHP? - php

Question

how could I clear the cache for the image instantly with my uploader? I'm currently trying this but isn't working. any suggestion? thank you !
ps : settings.php is the current page, and I'm using only one header location
the image is currently uploader some time, but not always, some time it doesn't work without a ctrl + maj + r
uploader code :
<?php
// UPLOAD FICHIER
if (isset($_POST['valider']))
{
if (isset($_FILES['avatar']) AND !empty($_FILES['avatar']['name']))
{
$tailleMax = 1000000;
$extensionsValide = array('jpg', 'png');
if ($_FILES['avatar']['size'] < $tailleMax)
{
$extensionsUpload = strtolower(substr(strrchr($_FILES['avatar']['name'], '.'), 1));
if (in_array($extensionsUpload, $extensionsValide))
{
$chemin = "../images/avatar/" . $_SESSION['id'] . "." . $extensionsUpload;
$resultat = move_uploaded_file($_FILES['avatar']['tmp_name'], $chemin);
$touxiang = $_SESSION['id'] . "." . $extensionsUpload;
$session = $_SESSION['id'];
if ($resultat)
{
$updateAvatar=$dbh->prepare("UPDATE members SET avatar = :avatar WHERE id = :id");
$updateAvatar->bindValue('avatar', $touxiang);
$updateAvatar->bindValue('id', $session);
$updateAvatar->execute();
header('Expires: Sun, 01 Jan 2014 00:00:00 GMT');
header('Cache-Control: no-store, no-cache, must-revalidate');
header('Cache-Control: post-check=0, pre-check=0', FALSE);
header('Pragma: no-cache');
header('Location: settings');
}
else
{
echo "<p class='review_wrong'>error.</p>";
}
}
else
{
echo "<p class='review_wrong'>wrong format. jpeg png.</p>";
}
}
else
{
echo "<p class='review_wrong'>File too large.</p>";
}
} // ISSET
}
?>
<div id="avatar_send_div">
<input id="upload_header" type="file" name="avatar">
<label for="upload_header" class="btn">Upload</label>
<input id="submit_header" type="submit" name="valider" value="Validate">
</div>
show image :
<?php
if (isset($_SESSION['id']) AND !empty($_SESSION['id']))
{
$id = $_SESSION['id'];
$req = $dbh->prepare('SELECT * FROM members WHERE id = :id');
$req->bindValue('id', $id);
$req->execute();
$userinfo = $req->fetch();
}
?>
<div id="settings_div_img">
<img id="settings_img" src="../images/avatar/<?php echo $userinfo['avatar'];?>">
</div>
db :

Answer 1

As others have stated in the comments, you can't really clear the cache with PHP, certainly not the cached assets (images, CSS files, etc). Assets are almost all the time served directly by the webserver.
The HTTP headers that you are setting with PHP will only affect the document being returned by your PHP script, which in your case is an HTML page. Also, sending headers does not guarantee that the cached document will be cleared (it's the job of the user's browser to do that).
So you are generating an HTML page with URLs pointing to images served by the webserver. To control the cache of these images, you mostly want to configure the webserver itself (Apache, NGINX, etc)
That again won't necessarily work if the user already has a previously cached image.
A common technique to go around that and avoid having to generate new image filenames is to append a version id to the image URL and change it as new versions of the image are uploaded.
So instead of having example.net/john.png you would generate example.net/john.png?v=1 and then when you upload a new image, you generate a new URL example.net/john.png?v=2. You can basically append anything to the query string, the goal is to generate a new URL that the browser hasn't seen before.
You will find more techniques here: Refresh image with a new one at the same url
I hope that helps.