PHP post_max_size overrides upload_max_filesize

Question

In my site host, I have seen (via phpinfo) that

• post_max_size = 8Mb
• upload_max_filesize = 16Mb

This led me to think that I should be able to upload as file as big as 16Mb. However, when I do this through a post method (as normal), post_max_size takes over and declares that I sent too much.

What is the method which permits sending a file as big as 16Mb ? GET - PUT - other ?

Hope someone can clarify this for me.

Simon

Answer 1

post_max_size:

• Sets max size of post data allowed. This setting also affects file upload
• To upload large files, this value must be larger than upload_max_filesize
• Generally speaking, memory_limit should be larger than post_max_size.
• PHP Default: 8M

upload_max_filesize:

• The maximum size of an uploaded file
• PHP Default: 2M

---

memory_limit > post_max_size > upload_max_filesize

PHP Default: 128M > 8M > 2M

By default, post_max_size should be 4 times greater than upload_max_filesize.
In turn memory_limit should be 16 times greater than post_max_size

Answer 2

By POST file uploads are done (commonly, there are also other methods). Look into the method attribute of the form which contains the file-upload field ;)

The lowest limit of any related setting supersedes a higher setting:

• post_max_size
• upload_max_filesize
• memory_limit

See Handling file uploads: Common Pitfals which explains this in detail and how to calculate the values.

Answer 3

change in php.ini max_input_vars 1000

Answer 4

upload_max_filesize is the limit of any single file. post_max_size is the limit of the entire body of the request, which could include multiple files.

Given post_max_size = 20M and upload_max_filesize = 6M you could upload up to 3 files of 6M each. If instead post_max_size = 6M and upload_max_filesize = 20M then you could only upload one 6M file before hitting post_max_size. It doesn't help to have upload_max_size > post_max_size.

It's not obvious how to recognize going over post_max_size. $_POST and $_FILES will be empty, but $_SERVER['CONTENT_LENGTH'] will be > 0. If the client just didn't upload any post variables or files, then $_SERVER['CONTENT_LENGTH'] will be 0.

Answer 5

Your server configuration settings allows users to upload files upto 16MB (because you have set upload_max_filesize = 16Mb) but the post_max_size accepts post data upto 8MB only. This is why it throws an error.

Quoted from the official PHP site:

1. To upload large files, post_max_size value must be larger than upload_max_filesize.

2. memory_limit should be larger than post_max_size

You should always set your post_max_size value greater than the upload_max_filesize value.

Answer 6

The normal method to send a file upload is POST, thus also post_max_size should be 16 Mb or more.

Incidentally, also memory_limit plays a role. It should be bigger than 16Mb, but since the default value is 128Mb, you won't see this problem. Example php.ini configuration:

post_max_size = 16M
upload_max_filesize = 16M
memory_limit = 128M

Change these value in php.ini if you've access to it, otherwise you can try to change them in an .htaccess file.

php_value upload_max_filesize 16M
php_value post_max_size 16M 

This will work only if the AllowOverride settings permit it. Otherwise, you've to ask to your hosting company.