Building File Uploaders with PHP 5 - Processing a file upload with PHP (
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Handling a file upload with PHP is a much simpler process than you might think. The core logic that must be implemented to perform this process is simply moving the user file that resides on a temporary directory of the web server to its final location.
Of course, as with many things in PHP programming, there are several ways to accomplish a file upload and each of them generally involves the use of different PHP native functions. However, in this particular case, I'm going to use the "move_uploaded_file()" function, which moves an uploaded file to a new location in the web server.
In simple terms, this function verifies that the target file has been uploaded by way of an HTTP POST request. And if this condition is true, the file in question is moved to the final location.
Now that you have a clear idea of how the "move_uploaded_file()" function works, pay close attention to the following PHP script. It uses this function to move an uploaded file to a predefined directory in the web server:
// basic example on uploading a file to the server via HTTP
if($_POST['send']){
// set upload directory (for Windows users)
$uploadDir='C:uploaded_files';
// set destination of uploaded file
$uploadFile=$uploadDir.basename($_FILES['userfile']['name']);
if(move_uploaded_file($_FILES['userfile']['tmp_name'],$uploadFile)){
echo 'The target file was successfully uploaded!';
}
else{
echo 'Error uploading target file!';
}
}
If you study the above PHP script in detail, you'll understand how it works. Basically, it checks to see if the corresponding file uploading form has been submitted and uses the aforementioned "move_uploaded_file()" PHP built-in function to move the uploaded file from its temporary directory to a predefined location in the web server.
In this case, I decided to move all of the valid uploaded files to the "C:uploaded_files" directory, which obviously is valid only for Windows users. If you're using another operating system, this option can be modified to fit your specific requirements.
Finally, if the uploaded file can't be moved to the predefined directory, a trivial error message is displayed on the browser. Of course, one of the most important things to highlight concerning the definition of the previous PHP script is the way that some elements of the $_FILES superglobal PHP array are utilized to complete the pertinent file uploading process. Now do you realize how the different pieces fit with each other when it comes to uploading files with PHP? I bet you do!
In addition, I'd like to wrap up this tutorial by showing you the complete source code of the two files that compose this basic file uploading PHP application so you can examine them more easily. Here they are:
(definition of 'upload_form.htm' file)
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>Uploading files with PHP</title>
<style type="text/css">
body{
padding: 0;
margin: 0;
background: #fff;
}
h1{
font: bold 16pt Arial, Helvetica, sans-serif;
color: #000;
text-align: center;
}
p{
font: normal 10pt Arial, Helvetica, sans-serif;
color: #000;
}
form{
display: inline;
}
#formcontainer{
width: 50%;
padding: 10px;
margin-left: auto;
margin-right: auto;
background: #eee;
border: 1px solid #666;
}
</style>
</head>
<body>
<h1>Uploading files with PHP</h1>
<div id="formcontainer">
<form enctype="multipart/form-data" action="upload_file.php" method="post">
<input type="hidden" name="MAX_FILE_SIZE" value="20000" />
<p>File to upload <input name="userfile" type="file" />
<input type="submit" name="send" value="Upload File" /></p>
</form>
</div>
</body>
</html>
(definition of 'upload_file.php' file)
if($_POST['send']){
// set upload directory (for Windows users)
$uploadDir='C:uploaded_files';
// set destination of uploaded file
$uploadFile=$uploadDir.basename($_FILES['userfile']['name']);
if(move_uploaded_file($_FILES['userfile']['tmp_name'],$uploadFile)){
echo 'The target file was successfully uploaded!';
}
else{
echo 'Error uploading target file!';
}
}
Before starting to upload files with PHP, remember to check your php.ini settings in addition to assigning the appropriate permissions to the corresponding destination directory in the web server.
Final thoughts
In this first tutorial of the series, I showed you how to build a basic file uploading application with PHP. It's something that can be useful if you're just starting to use this handy language or if you want to fill some possible gaps with reference to this topic.
However, when it comes to handling file uploads with PHP, I'm only scratching the surface. The application that I developed earlier lacks some important features, such as adequate control over the type and size of the file being uploaded as well as the inclusion of a solid error handling module.
Of course, all of these issues will be addressed in the next part. So you don't have any excuses to miss it!
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