Application of PHP functions in processing file uploads

File upload PHP function: move_uploaded_file(): Move the uploaded file file_exists(): Check whether the file exists is_uploaded_file(): Check whether the file is uploaded through HTTP POST getimagesize(): Get the size and type of the image file mime_content_type(): Get the MIME type of the file

Application of PHP function in file upload

File upload is a common function in Web development. PHP provides a variety of functions to easily handle file upload tasks.

Function

• move_uploaded_file(): Move the uploaded file from the temporary location to the specified location.
• file_exists(): Check whether the file exists.
• is_uploaded_file(): Check if the file was uploaded via HTTP POST.
• getimagesize(): Get the size and type of the image file.
• mime_content_type(): Get the MIME type of the file.

Practical Case: File Upload Script

We create a simple script that allows users to upload image files.

<?php
// 检查文件是否存在
if (isset($_FILES["image"])) {
    // 检查文件大小
    if ($_FILES["image"]["size"] > 2097152) {
        echo "文件过大，请上传小于 2MB 的图像。";
    } else {
        // 获取图像信息
        $imageInfo = getimagesize($_FILES["image"]["tmp_name"]);

        // 验证图像类型
        if ($imageInfo[0] > 1920 || $imageInfo[1] > 1920) {
            echo "图像尺寸太大，请上传小于 1920x1920 的图像。";
        } else if (!in_array($imageInfo[2], [IMAGETYPE_JPEG, IMAGETYPE_PNG])) {
            echo "图像格式不支持，请上传 JPEG 或 PNG 格式的图像。";
        } else {
            // 获取 MIME 类型
            $mimeType = mime_content_type($_FILES["image"]["tmp_name"]);

            // 移动文件
            if (move_uploaded_file($_FILES["image"]["tmp_name"], "uploads/" . $_FILES["image"]["name"])) {
                echo "图像上传成功。";
            } else {
                echo "图像上传失败。";
            }
        }
    }
}
?>

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