When the images are submitted by the image submission form the server/php receives the images and places them in a temporary folder configured by the server and PHP. The very first consideration when uploading images is the time it takes for the images to get to the server. Once the client clicks the submit button in the images form the images they have chosen within the image upload form begin to travel to your server/domain over the Internet.

There are a couple considerations to keep in mind with images traveling to your server/domain from a client. The first is the PHP timeout. PHP has a maximum execution time configuration designed to stop runaway computation processes. All hosts configure a maximum time that any PHP process can have to do what it needs to do. This is a precaution in place by the server to stop individual scripts from taking up all the resources on the server when it may look like the process may never stop. The time starts ticking on this process once the client clicks the submit button on the image upload form. The PHP execution timeout may actually last longer than the same amount of time in real time as the server may only count the time the server actually spends on the process.

The second consideration is the speed of connection between your client and you server/domain. The connection between the two is only as fast as the slowest portion of that connection. The slowest part of that connection is usually the clients Internet connection. This connection could be a slow "dialup" connection. In high traffic times the slowest portion of the pipe between your server/domain and your client could be your server's connection to the Internet.

Time is necessary to upload images to your server and the maximum execution time within PHP could affect this process. If the maximum execution time is exceeded the problem could be the Internet connection and/or the size of images uploaded to your site. When the maximum execution time is reached two things could happen. Your client will usually see a PHP error message stating that the maximum execution time has been exceeded if your host allows or has set PHP errors to be displayed...this is the usual case. Or your clients could see a blank white page if your host has PHP error display turned off within the PHP configuration file (php.ini file). When PHP is configured to not display errors the client browser is not displayed any errors if there happen to be any while processing. If this is the case the error could be found in your domains error log.

Once all of the images uploaded reach your server the images are placed in a temporary directory that is predetermined within the internal configurations of the server. Placing images within the temporary directory provides the next possible error that could happen in the image upload process. This is a very rare error and only happens when the server was not configured correctly to handle image uploads. The actual process running on the server handling the image upload process must have the correct "rights" to place those uploaded images into the temporary directory. This type of error usually does not happen with larger hosts. It usually only happens on server configured individually for a specific purpose. When this error happens the problem is at the server level...not within PHP. Errors within PHP are usually displayed to the browser. Errors at the server level are hardly ever displayed to the browser and they usually result in a blank white page displayed to the browser. Again not a very common error but one that can be considered once all others possible errors have been eliminated.

The information about the images uploaded is put into a variable within the PHP working environment called $_FILES. The Geodesic script then takes the information from the $_FILES array variable and begins processing the uploaded images and media into the Geodesic classified ad or auction system.

After the images are fully uploaded to the server the PHP environment "starts" the Geodesic script. The Geodesic script starts working its way through the $_FILES array that contains all the information about the files uploaded to the site. The script pulls information about each image one at a time and processes each image in turn working its way through the $_FILES array.

The first check of the files uploaded is the file size check. Each image is checked to make sure that is does not exceed the maximum file size set within the "max file size" set within the images configuration page of the admin tool. If the file size exceeds the maximum set the script will pass this particular image without any further computation and proceed to the next image in the $_FILES array. The image will not be attached to the listing currently being inserted by the client.

The next check run is to see if the image is within the accepted files list the admin has set within the allowed upload file type admin tool. The file type is checked by looking at the mime-type within the $_FILES array set for each particular uploaded file against the mime-type entered within the allowed file type admin tool. This is another place where an uploaded image will be rejected by the script. The mime-type for the uploaded image is embedded within the header of the file and is set within program that created the image or media. There are sometimes a few different mime-types for the same file type and you may have a client with one of these different mime-type headers yet have the same file type extension (for example ".jpg" at the end of the filename). When you have a client with unique/different mime-type the only way to possibly get the file allowed within the system is to get a copy of the file attempted by the client. You will need to manually insert the file into the allowed file type admin tool to allow the script to extract the new mime-type from the file and add that specific mime-type to the allowed file types list.

Once the mime-type has been determined to be within the allowed mime-types list the script then checks to see how the script should treat the uploaded file type. If the files mime-type is determined to not be within the accepted file types set within the admin processing on that file is stopped and the script moves onto the next file uploaded. This file will not be attached to the listing currently being created by the client.

Within the allowed upload file type admin tool the admin can determine how the file is treated when displayed on the client side within an auction or classified ad. The "image" file types like the jpeg or gif can be uploaded and the images displayed directly within the html with no problems. Other file types cannot be displayed directly within html efficiently. With these file types the admin can set an icon to display within the details of the auction or classified ad instead of the actual file itself. With these file types the client wishing to view these files can click on the icon and they will be prompted to download the image. If the file type uploaded is determined to be represented by an icon that file is then immediately uploaded to its final destination within the "images" directory. A reference to that uploaded file and the representative icon are then placed within the database in connection with the ad being inserted.

Before any file is moved into the "images" directory/folder the script attempts to find a filename not currently used within the images directory. The script randomly creates a 7 digit number and attempts to find a file by that name within the images directory. If no file of the same name is found this 7 digit number becomes the final filename for the uploaded file within the "images" directory.

If the file type uploaded is not represented by an icon and also not a jpeg file type the script immediately moves that file directly into the "images" directory. With file types that are not to be represented by an icon the image dimensions are discovered by the script and compared to the lead image or thumbnail dimensions set within the images configuration to determine what the thumbnail size dimensions should be. With the image file types that are not a jpeg type they are copied directly to the "images" directory with no thumbnail image created. PHP comes installed with GD Library within it. This is the image library used by PHP to create images and by the Geo script to create thumbnail images displayed while browsing and in the listing detail. This image library will only create jpeg images from other jpeg images. It cannot be used to resize other file types within Geo scripts. Other file types will most likely be added when they become more common image file types. But as a practice around the Internet 99% of images uploaded by clients is the jpeg image type. This is the image type that is most used by digital cameras.

The full size image height and width dimensions are compared to each other to determine the ratio between the two. This ratio is used to determine the height and width of the thumbnail image dimensions. The image is then moved by the script to the "images" directory to the filename found. Information about the image is then saved within the database that contains location information about the uploaded image, thumbnail dimensions and full size image dimensions.

If the lead image dimensions are larger than the thumbnail settings the lead image dimensions are the maximum thumbnail settings used when creating the thumbnail image. If the thumbnail dimensions are larger than the lead image dimensions the thumbnail dimension dimensions are used in creating the thumbnail image. If the lead image setting is not used the thumbnail width and height become the maximum dimensions of the thumbnail image.

Once the thumbnail size settings have been determined the script checks to see if the image is a jpeg type image. If it is a jpeg type of image the script will attempt to create a "thumbnail" sized image using the dimensions determined above. The script uses the GD image library that is configured to work with almost all PHP installations. To create the thumbnail image the script passes in the original image, the dimensions of the image to create from the original image and the quality setting to be used by GD library when creating that image. The resulting thumbnail image is then moved to the images directory as well as the full size image.

If the image is not a jpeg file type the script simply moves the file untouched to its final place within the images directory determined within the admin tool.

Once the images are moved the script then saves all the information about the images within the database with information that will tie the image to the ad or auction it should be attached to.