How to upload files and replace them in php-PHP Problem-php.cn

Home

Backend Development

PHP Problem

How to upload files and replace them in php

藏色散人

Feb 25, 2021 am 10:06 AM

php

php method to upload files and replace them: first create two files, namely "change.html" and "change.php"; then use "strrchar()" to process the files; then call to determine the file type function and convert it to lowercase; finally upload and replace the file.

How to upload files and replace them in php

The operating environment of this article: windows7 system, PHP7.1 version, DELL G3 computer

How to upload image files with php and Replace

First create two files: change.html and change.php

The form code of the change.html file is as follows:

<html>
<head>
<title>change file example.</title>
<meta charset="UTF-8">
</head>
<body>
<form method="post" action="changefile.php" enctype="multipart/form-data">
<table border=0 cellspacing=0 cellpadding=0 align=center width="100%">
<tr>
<td width=55 height=20 align="center">
<input type="hidden" name="MAX_FILE_SIZE" value="2000000" />
文件：
</td>
<td>
<input name="file" type="file" />
<input type="submit" name="submit" value="submit" />
</td>
</tr>
</table>
</form>
</body>
</html>

There are several requirements here Things to pay attention to, first look at this sentence

. Here we use the POST method. Some browsers also support the PUT method. Of course This requires modifications to the script, which I don't recommend. enctype="multipart/form-data must be set in the form, so that the server knows that the uploaded file contains regular form information. Remember, this must be set. In addition, a hidden field is needed to limit the maximum length of the uploaded file: < ;input type="hidden" name="MAX_FILE_SIZE" value="2000000">, the name here must be set to MAX_FILE_SIZE, the value is the maximum length of the uploaded file, the unit is B, here I limit it to 2M. Look at this sentence again ：, type="file" indicates the file type. In this way, a basic file upload interface is completed. Next, let’s talk about how to use PHP to process uploaded files. In addition, the maximum length of uploaded files set in your php.ini may affect your actual upload. Please modify it according to the actual situation. In addition, PHP uploads are first uploaded to a temporary directory and then moved to the specified directory. Yes, yes; the temporary directory can be modified as needed, or the default value can be used...

[Recommended learning: "PHP Video Tutorial"]

The following is the form Submit the change.php file code and take a look at what is in this file:

<?php
header("content-type:text/html;charset=utf-8");
 
/**
* @param string $oldfile 需要更换的文件名（包含具体路径名）
*/
function changeFile($oldfile){
$newfile = $_FILES[&#39;file&#39;][&#39;name&#39;];//获取上传文件名
$fileclass = substr(strrchr($newfile, &#39;.&#39;), 1);//获取上传文件扩展名,做判断用
$type = array("jpg", "gif", "bmp", "jpeg", "png");//设置允许上传文件的类型
if(in_array(strtolower($fileclass), $type)){
if(file_exists($oldfile)){
unlink($oldfile);
}
if(is_uploaded_file($_FILES[&#39;file&#39;][&#39;tmp_name&#39;])){//必须通过 PHP 的 HTTP POST 上传机制所上传的
if(move_uploaded_file($_FILES[&#39;file&#39;][&#39;tmp_name&#39;], $oldfile)){
//输出图片预览
echo "<center>您的文件已经上传完毕 上传图片预览: </center><br><center><img  src=&#39;$oldfile&#39; alt="How to upload files and replace them in php" ></center>";
}
}else{
echo "<center>上传失败，文件大于2M，请重新上传！</center>";
}
}else{
$text = implode(",", $type);
echo "<center>您只能上传以下类型文件：", $text, "</center><br>";
// echo "<script>alert(&#39;您只能上传以下类型文件：$text&#39;)</script>";
}
}
changeFile("./files/1.png");

You may be a little dizzy when you first read this~~, but if you look at it slowly, you will find that this thing is actually SO EASY!! Let’s talk about it first! Based on the following principle, this program takes uploading pictures as an example. It first determines whether the file type is an image format. If so, uploads the file, then uploads the file to and replaces the specified file. If the upload is successful, a preview of the uploaded picture will be output. Here are some functions in the program Let me give you some explanations. Let’s look at substr(strrchr($newfile, '.'), 1) first. What is the function of strrchar()? Let me give you an example. For example, for a picture file pic.jpg, we use strrchar( ) processing, strrchr(pic.jpg,'.'), it will return .jpg, do you understand? This function returns the string after the last position of the specified character in the string. With substr() we can get to jpg, so that we can get the suffix name of the file to determine whether the uploaded file conforms to the specified format. This program puts the specified format in an array, which can be added as needed during actual use.

Next, We call the function to determine the file type and convert it into lowercase strtolower($_FILES['file']['name']). There is a very key thing here $_FILES. This is a super global array that saves the required The processed form data can also be accessed directly if register_globals is turned on, but this is unsafe. Look at the upload interface just now . According to this form name, we can get a lot of information:

$_FILES['file']['name'] -- Get the file name

$_FILES['file']['tmp_name']--Get the temporary storage location

$_FILES['file']['size']--Get File size

$_FILES['file']['type']--Get the file MIME type

With this information, you can easily determine the file information. Isn't it very convenient? Next, there are some functions that need to be understood, file_exists()--determine whether the specified directory exists. If it does not exist, of course we cannot upload it (it seems like nonsense!), is_uploaded_file--determine whether the file has been uploaded through HTTP POST, move_uploaded_file--will upload The file is moved to the specified directory. If the upload is successful, we will output the preview, otherwise the output upload will fail...

The above is the detailed content of How to upload files and replace them in php. For more information, please follow other related articles on the PHP Chinese website!

Statement

The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

ACID vs BASE Database: Differences and when to use each.Mar 26, 2025 pm 04:19 PM

The article compares ACID and BASE database models, detailing their characteristics and appropriate use cases. ACID prioritizes data integrity and consistency, suitable for financial and e-commerce applications, while BASE focuses on availability and

PHP Secure File Uploads: Preventing file-related vulnerabilities.Mar 26, 2025 pm 04:18 PM

The article discusses securing PHP file uploads to prevent vulnerabilities like code injection. It focuses on file type validation, secure storage, and error handling to enhance application security.

PHP Input Validation: Best practices.Mar 26, 2025 pm 04:17 PM

Article discusses best practices for PHP input validation to enhance security, focusing on techniques like using built-in functions, whitelist approach, and server-side validation.

PHP API Rate Limiting: Implementation strategies.Mar 26, 2025 pm 04:16 PM

The article discusses strategies for implementing API rate limiting in PHP, including algorithms like Token Bucket and Leaky Bucket, and using libraries like symfony/rate-limiter. It also covers monitoring, dynamically adjusting rate limits, and hand

PHP Password Hashing: password_hash and password_verify.Mar 26, 2025 pm 04:15 PM

The article discusses the benefits of using password_hash and password_verify in PHP for securing passwords. The main argument is that these functions enhance password protection through automatic salt generation, strong hashing algorithms, and secur

OWASP Top 10 PHP: Describe and mitigate common vulnerabilities.Mar 26, 2025 pm 04:13 PM

The article discusses OWASP Top 10 vulnerabilities in PHP and mitigation strategies. Key issues include injection, broken authentication, and XSS, with recommended tools for monitoring and securing PHP applications.

PHP XSS Prevention: How to protect against XSS.Mar 26, 2025 pm 04:12 PM

The article discusses strategies to prevent XSS attacks in PHP, focusing on input sanitization, output encoding, and using security-enhancing libraries and frameworks.

PHP Interface vs Abstract Class: When to use each.Mar 26, 2025 pm 04:11 PM

The article discusses the use of interfaces and abstract classes in PHP, focusing on when to use each. Interfaces define a contract without implementation, suitable for unrelated classes and multiple inheritance. Abstract classes provide common funct

See all articles

Hot AI Tools

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress images for free

Clothoff.io

AI clothes remover

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Assassin's Creed Shadows: Seashell Riddle Solution

3 weeks agoByDDD

What's New in Windows 11 KB5054979 & How to Fix Update Issues

2 weeks agoByDDD

Where to find the Crane Control Keycard in Atomfall

3 weeks agoByDDD

Assassin's Creed Shadows - How To Find The Blacksmith And Unlock Weapon And Armour Customisation

1 months agoByDDD

Roblox: Dead Rails - How To Complete Every Challenge

3 weeks agoByDDD

Hot Tools

MantisBT

Mantis is an easy-to-deploy web-based defect tracking tool designed to aid in product defect tracking. It requires PHP, MySQL and a web server. Check out our demo and hosting services.

SAP NetWeaver Server Adapter for Eclipse

Integrate Eclipse with SAP NetWeaver application server.

MinGW - Minimalist GNU for Windows

This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

PhpStorm Mac version

The latest (2018.2.1) professional PHP integrated development tool

VSCode Windows 64-bit Download

A free and powerful IDE editor launched by Microsoft

Hot Topics

Where is the login entrance for gmail email?

7605

CakePHP Tutorial

1387

What is the format of the account name of steam

win11 activation key permanent

nyt connections hints and answers

127