How to Validate File Upload Types in PHP?

Uploading Specific File Formats in PHP with Conditional Validation

To limit file uploads to specific types, implement a conditional validation mechanism using the $_FILES global array and the in_array() function in PHP.

The code structure includes:

1. Extract the file's mime type (mime): Obtain the file's mime type from the $_FILES'file' array. This value represents the file's format, such as "image/jpeg" for JPEG images.
2. Define allowed file types (array): Create an array that contains the allowed file types' mime types. For example, if you want to allow only JPEG, GIF, and PDF files, your array could look like this:

$allowed = array('image/jpeg', 'image/gif', 'application/pdf');

3. Compare to allowed types (if-statement): Use the in_array() function to compare the file's mime type with the allowed types. This function returns 'true' if the mime type matches any entry in the $allowed array, and 'false' otherwise. Wrap this condition in an if-statement to check if the file type is not allowed.

Here's the modified code:

$mime = $_FILES['foreign_character_upload']['type']; // File mime type

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

If the file's mime type does not match any of the allowed types, the if-condition will be true and the $error and $error_message variables will be set accordingly. This enables you to handle the upload error and provide feedback to the user.

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