Returning white page? - php

Question

I have built somekinda image-api-key for my website but it doesn't seem to work. I get an blank page, returning nothing! Whats wrong? Greetings.
if(isset($_GET['key']) && !empty($_GET['key'])){
$query = " SELECT
*
FROM
table
WHERE
apikey = '". mysql_real_escape_string($_GET['key']) ."'
";
$mysqlquery = mysql_query($query);
if($mysqlquery){
if(mysql_num_rows($mysqlquery) > 0){
if(isset($_GET['type']) && isset($_GET['image'])){
if($_GET['type'] == "gif"){
if($_GET['image'] == "1"){
header('Content-type: image/gif');
echo file_get_contents('path/to/image/1.gif');
}
elseif($_GET['image'] == "2"){
header('Content-type: image/gif');
echo file_get_contents('path/to/image/2.gif');
}
elseif($_GET['image'] == "3"){
header('Content-type: image/gif');
echo file_get_contents('path/to/image/3.gif');
}
elseif($_GET['image'] == "4"){
header('Content-type: image/gif');
echo file_get_contents('path/to/image/4.gif');
}
elseif($_GET['image'] == "5"){
header('Content-type: image/gif');
echo file_get_contents('path/to/image/5.gif');
}
else
{
die('Could not load image');
}
}
else
{
die('Could not load image');
}
}
else
{
die('Could not load image');
}
}
else
{
die('Api key was not correct');
}
}
else
{
die('Mysql query failed');
}
}
else
{
die('No api key was set');
}

Answer 1

You need to check your error logs/ensure you have logging turned on as it sounds very much like PHP is throwing an error. (N.B.: If this is a production environment, be sure to turn logging back off afterwards.)
At a guess if could be one of the paths that's incorrect or you've already output some data prior to attempting to set a header, but the error logs should make it pretty obvious what the problem is.

Answer 2

If PHP is throwing certain kinds of errors such as syntax errors it will output an error message and terminate without any other output. However, if display_errors is turned off in php.ini then not even the error message will be output and you'll just get a blank screen.
Alternatively, if you're trying to send a file that doesn't exist after you've sent the image/gif header then this could also result in a blank page. Look at the headers that got sent back. If you got an image/gif content type header back then the code is reaching a point where it's trying to send an image. The fact you don't actually get an image would suggest that there's no image file to send.