1. Multiple attribute is added to the form field in the form form form to upload multiple files in a single field
2. To pass in information of multiple files in the form of array, you need to set the name property to: example: name = "post []"
3. Verify and save multiple files to disk as arrays
4. In the data receiver, loop through the receiving

<?php foreach ($value['poster'] as $img): ?> <?php endforeach ?>

//Upload multiple files in a single file domain
$pos_type = $_FILES['poster']['type'];
$pos_err = $_FILES['poster']['error'];
$pos_name = $_FILES['poster']['name'];
$pos_size = $_FILES['poster']['size'];
//All of the above are arrays of corresponding file information

$arr = array();//Used to store the path. To solve the problem of Notice:Array to string conversion
//Idea: to find out the problem, I directly connected the string with the array
//Solution: 1) create an empty array (here is $arr) to store the path of each uploaded image
			2)When traversing the file array, string("http://www.study4.com:81/unlode/")
			//Add to a new array (I'm here at $path)
			3)When traversing the array of file names, append each file name to the $path in
			4)Reuse implode("", $path);Method to name an array as a string
			5)Add the modified string to the $arr This is the case. $arr It's a one-dimensional array


$len = count($pos_name);
//Array of types used to verify uploaded pictures
$pos_arr = array("image/jpg","image/jpeg","image/gif","image/png");

for($i=0;$i<$len;$i++){ 
	$path = array("http://www.study4.com:81/unlode/");
	if(!(in_array($pos_type[$i], $pos_arr))){
		$GLOBALS['error_mes'] = "Wrong image upload type";
		continue;
	}
	if($pos_size[$i]<1*1024 || $pos_size[$i]>40*1024*1024){
		$GLOBALS['error_mes'] = "Picture file size is unreasonable";
		continue;
	}
	if($pos_err[$i] > 0){
		$GLOBALS['error_mes'] = $pos_err[$i];
	}else{
		if (file_exists("D:/www/www5/unlode/" . $_FILES["poster"]["name"][$i]))
    		{
    			$path[] = $_FILES["poster"]["name"][$i];
    			$path = implode("", $path);
    			$arr[] = $path;
      		  	echo $_FILES["poster"]["name"][$i] . " The file already exists. ";
    		}
    	else
    		{
        	// If the file does not exist in the upload directory, upload the file to the upload directory
        	move_uploaded_file($_FILES["poster"]["tmp_name"][$i], "D:/www/www5/unlode/" . $_FILES["poster"]["name"][$i]);
        	echo "Files stored in: " . "D:/www/www5/unlode/" . $_FILES["poster"]["name"][$i];
    		}	
	}
}