How Can I Determine the Content-Type of a File in PHP?

Determining the Content-Type of a File in PHP

When sending an email with an attachment, it is crucial to specify the correct content type for that file. This guides the email client in handling the file appropriately. In PHP, you can retrieve the content type using various methods.

Using 'finfo_file()' (Recommended)

If your PHP version supports the finfo extension, you can utilize 'finfo_file()' to obtain the file's mime type. Here's an example:

$finfo = finfo_open(FILEINFO_MIME_TYPE);
$contentType = finfo_file($finfo, $file);
finfo_close($finfo);

Using 'mime_content_type()'

An older alternative to 'finfo_file()' is the 'mime_content_type()' function. However, it may not be available in all PHP versions.

require_once 'upgradephp/ext/mime.php'; // Load the mime extension if necessary
$contentType = mime_content_type($file);

Fallback Options

If neither of the above methods provides a reliable result, you may consider using these fallback options:

• exec('file -b --mime-type ...'): Executes the 'file' command on the file to obtain its mime type. This method works on *NIX systems.
• exif_imagetype(): If the file is an image, this function can determine its mime type.
• 'upgradephp/ext/mime.php': Upgrade.php provides fallback mime_content_type() functions that can fill in the gaps for older PHP versions.

Example Usage

Here's an example that combines all these options:

function getFileMimeType($file) {
    $contentType = null;

    if (function_exists('finfo_file')) {
        $finfo = finfo_open(FILEINFO_MIME_TYPE);
        $contentType = finfo_file($finfo, $file);
        finfo_close($finfo);
    } elseif (function_exists('mime_content_type')) {
        require_once 'upgradephp/ext/mime.php';
        $contentType = mime_content_type($file);
    } elseif (is_file($file)) {
        // Executing 'file' command
    } elseif (@exif_imagetype($file)) {
        // Determining image mime type
    }

    return $contentType;
}

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