PHP file upload tutorial: How to upload files using HTML forms

PHP file upload tutorial: How to use HTML forms to upload files

In the process of website development, the file upload function is a very common requirement. As a popular server scripting language, PHP can implement the file upload function very well. This article will introduce in detail how to use HTML forms to complete file uploads.

1. HTML Form

First, we need to use an HTML form to create a file upload page. The enctype attribute needs to be set to "multipart/form-data" in the HTML form to allow file upload. The specific code is as follows:

<form action="upload.php" method="post" enctype="multipart/form-data">
  <input type="file" name="fileToUpload" id="fileToUpload">
  <input type="submit" value="上传文件" name="submit">
</form>

This form contains a file selection box and a submit button. The user can select the file to be uploaded, and then click the submit button to upload.

2. PHP file upload processing

Next, we need to create a PHP file to process file upload. The specific code is as follows:

<?php
$target_dir = "uploads/";
$target_file = $target_dir . basename($_FILES["fileToUpload"]["name"]);
$uploadOk = 1;
$imageFileType = strtolower(pathinfo($target_file,PATHINFO_EXTENSION));

// 检查文件是否是真正的文件类型
if(isset($_POST["submit"])) {
    $check = getimagesize($_FILES["fileToUpload"]["tmp_name"]);
    if($check !== false) {
        echo "文件是一个" . $check["mime"] . "文件。";
        $uploadOk = 1;
    } else {
        echo "文件不是一个图片文件。";
        $uploadOk = 0;
    }
}

// 检查文件是否已经存在
if (file_exists($target_file)) {
    echo "对不起，文件已存在。";
    $uploadOk = 0;
}

// 检查文件大小
if ($_FILES["fileToUpload"]["size"] > 500000) {
    echo "对不起，文件太大。";
    $uploadOk = 0;
}

// 允许特定文件格式上传
if($imageFileType != "jpg" && $imageFileType != "png" && $imageFileType != "jpeg"
&& $imageFileType != "gif" ) {
    echo "对不起，只允许JPG, JPEG, PNG & GIF 的文件上传。";
    $uploadOk = 0;
}

// 如果文件上传成功，将文件从临时目录移动到上传目录
if ($uploadOk == 0) {
    echo "对不起，您的文件未上传。";
} else {
    if (move_uploaded_file($_FILES["fileToUpload"]["tmp_name"], $target_file)) {
        echo "文件" . basename( $_FILES["fileToUpload"]["name"]). "上传成功。";
    } else {
        echo "对不起，上传过程中发生了错误。";
    }
}
?>

In this PHP file, we first need to specify the target folder for file upload, here we specify it as the uploads folder. Next, we need to do some checking and verification of file uploads. For example, we need to check whether the file is a real file type, whether the file already exists, whether the file size is appropriate, etc. If the file passes all checks and validations, we can move the file from the temporary directory to the upload directory.

3. Notes

When using PHP to upload files, you need to pay attention to the following issues:

1. The server must have the target folder with write permission.

2.enctype attribute must be set to "multipart/form-data" so that file upload can be supported.

3. The type attribute of the input element must be set to "file" so that the file selection box can be created.

4.PHP only allows the maximum upload file size to be 2MB by default, which can be modified by modifying the upload_max_filesize and post_max_size parameters in the php.ini file.

5.PHP only allows uploading some common file types by default, such as JPG, PNG, GIF, etc. You can add other file types by modifying the upload_file_types parameter in the php.ini file.

4. Summary

File upload is a very common requirement in website development. This article introduces the methods of HTML form and PHP file upload processing, hoping to help readers better implement the file upload function. . When uploading files, you need to pay attention to security issues to avoid problems such as malicious file uploads and file injection. At the same time, it is also recommended that readers learn more about file uploading in order to better deal with various file uploading problems.

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