PHP upload size bigger than post size.
Add too your php.ini file
file_uploads = On
; Must be greater than or equal to upload_max_filesize
post_max_size = 100M
; Maximum allowed size for uploaded files.
upload_max_filesize = 100M
Maximum upload limits
The upload limit does not guarantee an upload will complete — only that it isn't rejected by the server.
Uploads beneath the limit can still fail because of:
Upload speed, which can cause timeouts from your PHP script or your browser
Your account's resource availability, which can cause large files to fail