织梦cms如何阻止上传php代码

<script>
function checkFileType(input) {
    var file = input.files[0];
    var allowedTypes = ['image/jpeg', 'image/png', 'application/pdf']; // 允许的文件类型
    var allowedExtensions = ['jpg', 'jpeg', 'png', 'pdf']; // 允许的文件扩展名
    var ext = file.name.split('.').pop().toLowerCase();

    if (allowedTypes.indexOf(file.type) === -1 || allowedExtensions.indexOf(ext) === -1) {
        alert('只允许上传图片和PDF文件！');
        input.value = '';
        return false;
    }
    return true;
}
</script>

<input type="file" onchange="checkFileType(this)">

<?php
$allowedTypes = ['image/jpeg', 'image/png', 'application/pdf'];
$allowedExtensions = ['jpg', 'jpeg', 'png', 'pdf'];

$file = $_FILES['file'];
$fileType = $file['type'];
$fileName = $file['name'];
$fileExtension = pathinfo($fileName, PATHINFO_EXTENSION);

if (!in_array($fileType, $allowedTypes) || !in_array($fileExtension, $allowedExtensions)) {
    echo '只允许上传图片和PDF文件！';
    exit;
}

// 检查文件内容
$content = file_get_contents($file['tmp_name']);
if (preg_match('/<\?php/i', $content)) {
    echo '文件包含PHP代码，上传失败！';
    exit;
}

// 文件验证通过，进行上传操作
// ...
?>