How to Validate Uploaded File Types in PHP with `in_array()`?

Uploading Specified File Types with PHP

In web applications, allowing users to upload files requires careful consideration of security and content validation. When you want to restrict uploads to specific file types, PHP provides a solution through the in_array() function.

Problem:

You wish to create an if statement in PHP to validate uploaded files and allow only files of the following types: jpg, gif, and pdf. The code below requires the appropriate structuring of the if statement.

$file_type = $_FILES['foreign_character_upload']['type']; //returns the mimetype

if(/*$file_type is anything other than jpg, gif, or pdf*/) {
  $error_message = 'Only jpg, gif, and pdf files are allowed.';
  $error = 'yes';
}

Solution:

To ensure files uploaded conform to your specifications, create an array of allowed file types and utilize in_array() to determine whether the uploaded file's mimetype is included in the array.

$file_type = $_FILES['foreign_character_upload']['type']; //returns the mimetype

$allowed = array("image/jpeg", "image/gif", "application/pdf");
if(!in_array($file_type, $allowed)) {
  $error_message = 'Only jpg, gif, and pdf files are allowed.';
  $error = 'yes';
}

By comparing the file type against the predefined list of allowed types, this revised if statement effectively prevents uploads of non-compliant files.

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