Check if a file extension is not changed before uploading in php

Question

I have to upload a pdf type of file only. There are different ways by which we can check the extension of the file like $_FILES['files']['type'] or pathinfo() function. But what if a person changes the extension of the file before uploading. Example. If a person changes a png file from image.png to image.pdf. Then how can I check that the uploaded file is not a pdf?

Answer 1

try this

echo mime_content_type('form.pdf');

check more info in http://php.net/manual/es/function.mime-content-type.php

EDIT:

I rename a .zip file to .pdf file

if(isset($_FILES['archivo']) && is_uploaded_file($_FILES['archivo']['tmp_name']))
{

 $archivo = $_FILES['archivo']['tmp_name'];
 $archivo_name = $_FILES['archivo']['name'];

echo mime_content_type($archivo);

 move_uploaded_file($archivo, "upload/" . $archivo_name);

}

the script above print application/zip

Then you can do something like this:

if (mime_content_type($_FILES['archivo']['tmp_name']) == 'application/pdf') {
//ok is a pdf
}