How to limit file uploads to a specific file type (e.g., image, PDF) in PHP?

To limit file uploads to a specific file type in PHP, you can use the following steps:

Add a file input field in your HTML form:

<form action="upload.php" method="POST" enctype="multipart/form-data">
  <input type="file" name="fileUpload">
  <input type="submit" value="Upload">
</form>

Create a PHP script (e.g., upload.php) to handle the file upload:

<?php
$allowedFileTypes = ['image/jpeg', 'image/png', 'application/pdf']; // Allowed file types

if ($_FILES['fileUpload']['size'] > 0) {
    $tempFile = $_FILES['fileUpload']['tmp_name'];
    $fileType = $_FILES['fileUpload']['type'];

    if (in_array($fileType, $allowedFileTypes)) {
        $uploadDir = 'uploads/'; // Directory to store uploaded files
        $uploadFile = $uploadDir . basename($_FILES['fileUpload']['name']);

        if (move_uploaded_file($tempFile, $uploadFile)) {
            echo 'File uploaded successfully.';
        } else {
            echo 'Error uploading file.';
        }
    } else {
        echo 'Invalid file type. Only JPEG, PNG, and PDF files are allowed.';
    }
} else {
    echo 'No file selected.';
}
?>

In the PHP script, check if a file is selected and its size is greater than 0.
Get the temporary file name and file type using $_FILES['fileUpload']['tmp_name'] and $_FILES['fileUpload']['type'].
Check if the file type is present in the $allowedFileTypes array using in_array() function.
If the file type is allowed, specify the directory where you want to upload the files ($uploadDir).
Move the uploaded file from the temporary location to the desired directory using move_uploaded_file() function.
Display appropriate success or error messages based on the file upload result.

Note: Make sure the directory where you want to upload files has the necessary write permissions so that PHP can move the files to that directory.