Notes

You can create file upload functionality by using PHP. Initially files are uploaded into a temporary directory of web server and then relocated to a target destination folder by a PHP function.

File upload parameters, i.e. upload_tmp_dir, upload_max_filesize are default set into PHP configuration file php.ini.

Create an HTML Upload-File Form
<form action="" method="post" enctype="multipart/form-data" name="form1">
<input type="file" name="resume" id="resume">
<input type="submit" name="SubmitBtn" id="SubmitBtn" value="Upload Resume">
</form>
HTML form attribute (enctype=’multipart/form-data‘) is required to upload a file.
Creating an PHP File Upload Script
<?php
ifisset($_POST["SubmitBtn"])){

$fileName=$_FILES["resume"]["name"];
$fileSize=$_FILES["resume"]["size"]/1024;
$fileType=$_FILES["resume"]["type"];
$fileTmpName=$_FILES["resume"]["tmp_name"];

if($fileType=="application/msword"){
if($fileSize<=200){

//New file name
$random=rand(1111,9999);
$newFileName=$random.$fileName;

//File upload path
$uploadPath="testUpload/".$newFileName;

//function for upload file
if(move_uploaded_file($fileTmpName,$uploadPath)){
echo "Successful";
echo "File Name :".$newFileName;
echo "File Size :".$fileSize." kb";
echo "File Type :".$fileType;
}
}
else{
echo "Maximum upload file size limit is 200 kb";
}
}
else{
echo "You can only upload a Word doc file.";
}
}
?>
By using the PHP global $_FILES array you can upload file from a client computer to the web server.
• $_FILES[“file”][“name”] – uploaded file name
• $_FILES[“file”][“type”] – uploaded file type
• $_FILES[“file”][“size”] – uploaded file size in bytes
• $_FILES[“file”][“tmp_name”] – uploaded file temporary file name
• $_FILES[“file”][“error”] – the error code resulting from the file upload
Saving the Uploaded File
The examples above create a temporary copy of the uploaded files in the PHP temp folder on the web server and then PHPmove_uploaded_file() function relocate uploaded file from temp directory to a our target destination.
The temporary copied file auto deleted when the script execution ends.


Thumbnail
function make_thumb($src, $dest, $desired_width) {

/* read the source image */
$source_image = imagecreatefromjpeg($src);
$width = imagesx($source_image);
$height = imagesy($source_image);

/* find the "desired height" of this thumbnail, relative to the desired width */
$desired_height = floor($height * ($desired_width / $width));

/* create a new, "virtual" image */
$virtual_image = imagecreatetruecolor($desired_width, $desired_height);

/* copy source image at a resized size */
imagecopyresampled($virtual_image, $source_image, 0, 0, 0, 0, $desired_width, $desired_height, $width, $height);

/* create the physical thumbnail image to its destination */
imagejpeg($virtual_image, $dest);
}




For more details please visit

https://code.tutsplus.com/articles/how-to-dynamically-create-thumbnails--net-1818