What are common issues with uploading files in PHP, specifically related to the $_FILES array?

One common issue with uploading files in PHP related to the $_FILES array is not setting the correct form attribute 'enctype' to 'multipart/form-data'. This attribute is required when submitting forms that include file uploads. Without this attribute, PHP will not populate the $_FILES array with the uploaded file information. 

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

In the PHP file (upload.php), you can access the uploaded file information through the $_FILES array:

```php
<?php
if ($_FILES['file']['error'] === UPLOAD_ERR_OK) {
    $fileTmpPath = $_FILES['file']['tmp_name'];
    $fileName = $_FILES['file']['name'];
    // Process the uploaded file
} else {
    echo "File upload failed with error code: " . $_FILES['file']['error'];
}
?>

Keywords

File upload $_FILES array file size limit file type validation temporary directory.

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