Filter file upload php

Restrict Upload File Type In PHP (Allow Only Certain File Types)

Welcome to a quick tutorial on how to restrict the upload file type in PHP. So you have a project that allows users to upload their files, but want to allow only certain file extensions? Maybe images for the profile picture, or documents for importing?

To restrict the upload file types in PHP:

1. We can set the accept attribute in the HTML file input field.
4. Then save the uploaded file in PHP, only if it is an allowed file type.
5. $accept = [«jpg», «png», «gif», «webp»];
6. $ext = strtolower(pathinfo($_FILES[«up»][«name»], PATHINFO_EXTENSION));
7. if (in_array($ext, $accept))

That covers the quick basics, but read on for more detailed examples!

TLDR – QUICK SLIDES

TABLE OF CONTENTS

UPLOAD FILE TYPE RESTRICTION

All right, let us now get into the examples of how to restrict the upload file type in PHP.

EXAMPLE 1) RESTRICT BY FILE EXTENSION

1A) HTML UPLOAD FORM

As in the introduction, we only have to set the accept attribute in the file input field. But take note of how we define the file restriction here – .txt,.pdf,.doc,.docx . Yes, that is a list of file extensions, separated by commas.

1B) PHP UPLOAD HANDLER

 // (B) FLAGS & "SETTINGS" // (B1) ACCEPTED & UPLOADED MIME-TYPES $accept = ["txt", "pdf", "doc", "docx"]; // all lower case $upext = strtolower(pathinfo($_FILES["upfile"]["name"], PATHINFO_EXTENSION)); // (B2) SOURCE & DESTINATION $source = $_FILES["upfile"]["tmp_name"]; $destination = $_FILES["upfile"]["name"]; // (C) SAVE UPLOAD ONLY IF ACCEPTED FILE TYPE if (in_array($upext, $accept)) < echo move_uploaded_file($source, $destination) ? "OK" : "ERROR UPLOADING"; >else

1. If not file is uploaded, we show an error message.
2. Define the list of accepted file extensions in $accept , and “extract” the uploaded file extension from $_FILES[«upfile»] .
3. Save the upload, only if it is an accepted file extension.

That’s all. But some of you guys may be thinking “this is so dumb”, “we have already set the restriction in HTML”, and “this is unnecessary”. Well, no. HTML can be easily changed by anyone who knows how to work with the developer’s console. A check on server-side PHP is still required.

EXAMPLE 2) RESTRICT BY MIME-TYPE

2A) HTML UPLOAD FORM

Look no further, this is also “just an HTML upload form”, but take note of the difference here – accept=»image/*» . Yes, we are restricting by the file MIME type here now. Not going to bore you into tears, I will just leave a link below if you want to learn more about MIME types.

2B) PHP UPLOAD HANDLER

 // (B) FLAGS & "SETTINGS" // (B1) ACCEPTED & UPLOADED MIME-TYPES $accept = ["image/jpeg", "image/png", "image/gif", "image/webp"]; $upmime = strtolower($_FILES["upfile"]["type"]); // (B2) SOURCE & DESTINATION $source = $_FILES["upfile"]["tmp_name"]; $destination = $_FILES["upfile"]["name"]; // (C) SAVE UPLOAD ONLY IF ACCEPTED FILE TYPE if (in_array($upmime, $accept)) < echo move_uploaded_file($source, $destination) ? "OK" : "ERROR UPLOADING"; >else

Look no further again, this is just about the same as the previous example. Except that we are checking against the uploaded file MIME-type instead of the file extension now.

DOWNLOAD & NOTES

Here is the download link to the example code, so you don’t have to copy-paste everything.

SUPPORT

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EXAMPLE CODE DOWNLOAD

Click here for the source code on GitHub gist, just click on “download zip” or do a git clone. I have released it under the MIT license, so feel free to build on top of it or use it in your own project.

EXTRA BITS & LINKS

That’s all for the tutorial, and here is a small section on some extras and links that may be useful to you.

WHICH IS BETTER? EXTENSION OR MIME-TYPE?

Both works. But if I have to choose, I will say that the MIME type is “more secure”. In the sense that file extensions can be easily changed, but the MIME type is more roundabout. Either way, you can impose a check on both the file extension and MIME type… If you really want to go that far.

LINKS & REFERENCES

INFOGRAPHIC CHEAT SHEET

THE END

Thank you for reading, and we have come to the end. I hope that it has helped you to better understand, and if you want to share anything with this guide, please feel free to comment below. Good luck and happy coding!

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Solved: html filter file upload

The main problem related to HTML filter file upload is that it can be easily bypassed. HTML filters are designed to block certain types of files from being uploaded, but they can be bypassed by changing the file extension or by using a tool to edit the file header. This means that malicious files can still be uploaded, potentially leading to security vulnerabilities and data breaches. Additionally, HTML filters are not able to detect malicious code within a file, so even if a malicious file is blocked from being uploaded, it could still contain malicious code that could be executed on the server.

1. This line creates an HTML form with the action attribute set to “upload.php” and the method attribute set to “post”, as well as setting the enctype attribute to “multipart/form-data”:

Filtering and validating file importance

Filtering and validating file importance in HTML is a process of ensuring that only the necessary files are uploaded to a web page. This can be done by setting up rules and parameters for the types of files that can be uploaded, such as file size, type, or extension. Additionally, HTML forms can be used to validate user input before it is submitted to the server. This helps ensure that only valid data is accepted and prevents malicious code from being executed on the server. Finally, it is important to use secure methods for uploading files such as using HTTPS or SFTP protocols instead of FTP.

How do I restrict file types in HTML

The HTML standard does not provide a way to restrict file types when using an element. However, you can use JavaScript to check the file type before it is uploaded.

To do this, you can use the FileReader API to read the contents of the file and then check its type. If it is not one of the allowed types, you can prevent it from being uploaded by calling preventDefault() on the event object passed into your change handler.

You can also use HTML5’s accept attribute on your element to specify which types of files are allowed. This will cause a browser-specific dialog box to appear when a user tries to upload a file that is not in one of the accepted formats.

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