Uploading files Dr. Steven Bitner Uploading files (chapter 19) - PowerPoint PPT Presentation

Uploading files Dr. Steven Bitner

Uploading files (chapter 19)  http://kc-sce- sphp01.kc.umkc.edu/~bitners/dashboard.php

How does that work  Several different approaches  We'll only cover one to avoid confusion  Steps follow

Server settings  First things first  Use phpinfo() again  http://kc-sce-sphp01.kc.umkc.edu/~bitners/junk.php  Look for:  file_uploads  max_file_uploads  upload_max_filesize

Another superglobal  $_GET,$_POST,$_REQUEST, and $_SERVER have a friend  Called $_FILES  Just like the others, it is created at the right time

Interface with users  http://kc-sce- sphp01.kc.umkc.edu/~bitners/code.php?page=dashboard.p hp  Two elements of note <input type = "hidden" name = "MAX_FILE_SIZE" value = "2000000" /> <input type = "file" name = "bestFileEver" />

Submit  Of course don't forget your <form> and <button> tags  Make sure that your form method is POST and that you set the action attribute to the file you intend to use for uploading <form action = "uploadMe.php" method = "POST" enctype= "multipart/form-data">

enctype?  The enctype (encoding type) attribute for the form tag tells the browser that you will be including different encoding formats  This is similar to the multipart information needed for mailing an attachment or including HTML in an email  Without this attribute properly set, your script will fail

$_FILES is alive  When the user clicks submit, the $_FILES superglobal arrray is created in much the same manner as $_POST is created

Where to store files  Server directory – The book way (more sample code)  pros:  easiest approach, since the file system does this automatically  less open to injection attacks  cons:  Much harder to control access  File itself is stored separately from metadata  Database – this is the way we'll discuss  pros:  Have total control over who can view  cons:  More complex to program  Injection attacks can happen if you don't use prepared statements

Database storage of files  Need a database table for storing files with:  name – this will store the name of the file  CHAR or VARCHAR  size – to store the size of the file  INT  $_FILES['size'] is a quick bit of error checking to make sure that a file was uploaded  type – in order to send the appropriate header, or include the correct data type in the form src attribute  CHAR or VARCHAR  content – the file itself  any member of the BLOB family  TINYBLOB – up to 2 8 bytes = 256B  BLOB – up to 2 16 bytes = 64KB  MEDIUMBLOB – up to 2 24 bytes = 16MB  LONGBLOB – up to 2 32 bytes = 4GB

Uploading  Like all of PHP , you can choose a functional or an object oriented approach  You can hard code this functionality inline, but then the code is not re-usable  http://kc-sce- sphp01.kc.umkc.edu/~bitners/code.php?page=resources/u ploader.php

Did it work?  Check your database table directly  kc-sce-sphp01.kc.umkc.edu:8888  If it's in there, you're almost done

Viewing  We don't store files for the sake of wasting disk space  Once again two approaches  Display by encoding the data from the db and using the following image tag <img src="data:image/jpeg;base64,ENC_FILE" />  ENC_FILE above is the value returned from base64_encode ($file);

More common approach  Use a script as an image src  Send header from the script <img src="showImage.php?id=8" />  Tons of examples online  Essentially, send the appropriate headers and then echo the content from the database