PHP中文件上传的方法通常是通过HTML的表单来实现。上传文件时，需要使用enctype="multipart/form-data"属性来指定表单数据编码类型为multipart/form-data。
以下是一个简单的文件上传表单示例：
<form action="upload.php" method="post" enctype="multipart/form-data"> Select image to upload: <input type="file" name="fileToUpload" id="fileToUpload"> <input type="submit" value="Upload Image" name="submit"></form>在upload.php文件中，可以使用$_FILES超全局数组来获取上传的文件信息。以下是一个简单的文件上传处理示例：
<?php$target_dir = "uploads/";$target_file = $target_dir . basename($_FILES["fileToUpload"]["name"]);$uploadOk = 1;$imageFileType = strtolower(pathinfo($target_file, PATHINFO_EXTENSION));// Check if file already existsif (file_exists($target_file)) { echo "Sorry, file already exists."; $uploadOk = 0;}// Check file sizeif ($_FILES["fileToUpload"]["size"] > 500000) { echo "Sorry, your file is too large."; $uploadOk = 0;}// Allow certain file formatsif ($imageFileType != "jpg" && $imageFileType != "png" && $imageFileType != "jpeg" && $imageFileType != "gif") { echo "Sorry, only JPG, JPEG, PNG & GIF files are allowed."; $uploadOk = 0;}// Check if $uploadOk is set to 0 by an errorif ($uploadOk == 0) { echo "Sorry, your file was not uploaded.";// if everything is ok, try to upload file} else { if (move_uploaded_file($_FILES["fileToUpload"]["tmp_name"], $target_file)) { echo "The file ". htmlspecialchars( basename( $_FILES["fileToUpload"]["name"])). " has been uploaded."; } else { echo "Sorry, there was an error uploading your file."; }}?>以上代码会将上传的文件保存到uploads/目录，并输出上传成功或失败的信息。在实际项目中，还可以添加更多的文件验证和安全检查。
