php - 仅发布图像文件或允许发布无文件

Question

如果应该发布的文件不是图像，或者在没有选择文件时返回 true，javascript 中是否有办法发布警报？

Answer 1

以下工作正常。在表单上提交 php 代码

<?php

$fileType = $_FILES['avatarfile']['type'];
if(isset($_POST['submit']) && (($_FILES['avatarfile']['type'] == "image/gif")
|| ($_FILES['avatarfile']['type'] == "image/jpeg")
|| ($_FILES['avatarfile']['type'] == "image/pjpeg") || ($_FILES['avatarfile']['type'] == "image/bmp") || ($_FILES['avatarfile']['type'] == "image/png") || $fileType == NULL))
{

$query="insert into ...)";
header('Location:something.php');
}
else { 
echo "The file you tried to upload is not an image";
}
?>