How Can I Efficiently Validate File Extensions in PHP?

Ensuring Accurate File Extension Checking

File extension verification is crucial when handling file uploads in PHP. One common method involves using the pathinfo function, as demonstrated in the query:

$filename = $_FILES['video_file']['name'];
$ext = pathinfo($filename, PATHINFO_EXTENSION);
if ($ext !== 'gif' || $ext !== 'png' || $ext !== 'jpg') {
    echo 'error';
}

However, this approach may not be optimal when supporting a wider range of extensions. Consider the case where you allow 20 different extensions:

if ($ext !== 'gif' || $ext !== 'png' || $ext !== 'jpg' || ...) {
    // ...
}

Such code would be verbose and potentially inefficient. An alternative method involves utilizing an array of allowed extensions:

$allowed = array('gif', 'png', 'jpg');
$filename = $_FILES['video_file']['name'];
$ext = pathinfo($filename, PATHINFO_EXTENSION);
if (!in_array($ext, $allowed)) {
    echo 'error';
}

This approach simplifies the code and improves efficiency by reducing the number of comparisons required. By checking if the extension exists in the $allowed array, you can quickly validate its validity.

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