PHP file upload main code explanation_php basics

Copy code The code is as follows:

if($_FILES[ 'myfile']['name'] != '') {
if($_FILES['myfile']['error'] > 0) {
echo "Error status:" . $_FILES[' myfile']['error'];
} else {
move_uploaded_file($_FILES['myfile']['tmp_name'], "uploads/" . $FILES['myfile']['name'] );
echo "<script>alert(Upload successful!);</script>";
}
} else{
echo "<script>alert(Please upload the file!);</script>";
}
?>

Description:

Before explaining this code, we need to understand the following knowledge.

$_FILES['myfile']['name'] refers to the name of the uploaded file
$_FILES['myfile']['type'] refers to the type of the uploaded file
$_FILES[ 'myfile']['size'] refers to the size of the uploaded file, in bytes (B)
$_FILES['myfile']['tmp_name'] refers to the temporary copy of the uploaded file stored in the server The file name will be automatically destroyed after the file is moved to the specified directory.
$_FILES['myfile']["error"] refers to the status code of errors that may occur during file upload. The meaning of each status will be explained later.

Understanding this, let’s take a look at the code of upload.php.

First of all, myfile in $_FILES['myfile']['name'] refers to the name value of the file tag uploaded in the above HTML page. Based on this, we can know which input submitted the file we are processing. of.

Then let’s check whether $_FILES['myfile']['name'] is empty. Based on this, we can know whether the user has uploaded files and perform different operations.

If the file is uploaded and the status is 0, it means the upload is successful. We can use the move_uploaded_file method to store the uploaded file in the specified directory. The above example refers to moving the uploaded file to the uploads folder in the same directory. , this path is relative to the directory relative to the PHP file (upload.php).

For example, if we want to move the uploaded file to a folder called user one level above upload.php, we can write like this: move_uploaded_file ($_FILES['myfile']['tmp_name'], ". /user/". $FILES['myfile']['name']), this method is very convenient and flexible to use. In this way, a file is uploaded to the server, and you can open the directory in the server to view the file.