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PHP+SQL4.

File handling basicsFile-based "database"File-based guestbook

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V 1.0 OE NIK 2013

PHP+SQL4.

File handling basicsFile-based "database"File-based guestbook

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Basic principles• File paths:

document_root (<a href=‘/path/to/file’>) vsphp disk root ($path=‘/path/to/file’)

• File handle (file variable), file modes• Concurrent file access, race condition bug• Permissions (www-data/IUSR vs ftp-user)• EOL byte(s)?• EOF byte?

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Functions• file_exists($path), fopen($path, $mode), fclose($fp),

feof($fp)• fwrite($fp, $s)=fputs($fp, $s)=binary-safe write • fgetc($fp), fgets($fp), fread($fp, $len), rewind($fp)• file($path)• fpassthru($fp), readfile($path)• realpath($path), basename($path), unlink($path),

pathinfo($path), filesize($path)

$fname="path/to/file.txt";$cont=file_get_contents($fname);$cont.="hellobello";file_put_contents($fname, $cont);

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Usage of files (one row contents)<?php$fp=fopen("welcome.txt","wb"); //file handlefwrite($fp, "Hello world\n"); //same: fputs()fclose($fp); //close file

$fp=fopen("welcome.txt","r");$str=fgets($fp); //fread: not the same!echo $str;fclose($fp);?>

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File modesModes Description

r Read only. Starts at the beginning of the file

r+ Read/Write. Starts at the beginning of the file

w Write only. Opens and clears the contents of file; or creates a new file if it doesn't exist

w+ Read/Write. Opens and clears the contents of file; or creates a new file if it doesn't exist

a Append. Opens and writes to the end of the file or creates a new file if it doesn't exist

a+ Read/Append. Preserves file content by writing to the end of the file

x Write only. Creates a new file. Returns FALSE and an error if file already exists

x+ Read/Write. Creates a new file. Returns FALSE and an error if file already exists

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Perfect use<?php$handle = @fopen("/tmp/inputfile.txt", "r");if ($handle) { while (($buffer = fgets($handle, 4096)) !== false) { echo $buffer; } if (!feof($handle)) { echo "Error: unexpected fgets() fail\n"; } fclose($handle);}?>

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WRONG use$file = fopen("welcome.txt", "r");while(!feof($file)) { //Endless infinite loop!!!!!! echo fgets($file)."<br />";}fclose($file);

Alternative solution:$file = fopen("welcome.txt", "r") or die("Unable to open file!");

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Example: DOWNLOAD.PHP

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PHP+SQL4.

File handling basicsFile-based "database"File-based guestbook

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File format• The entities are typically in the separate rows of the file,

the data fields are usually separated by some special character ( \t ; , | )

• The only problem is that if a data field contains \n or \t we forbid these (we could substitute with special letters (weak solution), or we could properly use some special escaping (strong solution, but difficult) )

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File I/O• $path=‘database.txt’;

• $database=array();$rows_array=file($path, FILE_IGNORE_NEW_LINES);foreach ($rows_array as $key=>$row) {

$database[]=explode("\t", $row);} //we could use row-by-row operations

• $cont="";foreach ($database as $one_record) {

$cont.=implode("\t", $one_record)."\n";}file_put_contents($path, $cont); // we could use … …

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HOMEWORK (FOR POINTS!!!)

• Find out a topic, we need ONE entity with at least FIVE data fields that we want to store (e.g. topic: DVD rental; entity: movies; data fields: title, year, director, price, number_of_copies)

• Create a text file that stores 10 entities• Create a PHP script that reads the text file and

displays the entities in an HTML table• Find out and program 5 simple questions where you

can use simple programming theorems (e.g. What is the most expensive movie, how much movies do we have from 2001), the questions and answers must be displayed below the main table

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HOMEWORK (FOR POINTS!!!)

• Using the original dataset as a source, randomly generate 20 other entities (e.g. 20 random movies) into another array, and display them below the simple questions & answers

• Find out and program 3 complex questions that require BOTH arrays (e.g. Generate the union/intersection, or use come complex programming theorems/tasks !)

• Create a PDF documentation describing the task you chose and the 8 questions you found out. Do not describe the algorithms step-by-step, but write down which programming theorems did you use in the different parts of the code

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HOMEWORK (FOR POINTS!!!)

• Deadline: 17th of March, midnight!• Email to szabo.zsolt@nik.uni-obuda.hu , the subject

must contain the letters [PHP] , the email text must contain your name and your neptun code

• The email must contain a ZIP/ARJ/RAR/GZ/7Z/XZ file (fullname_neptuncode.zip) that contains:• The full PHP source

(HTML+CSS can be used, but not required)• The example TXT file with the 10 entities• The full documentation in PDF form (use some

nice formatting, header, footer, etc – must look pretty! )

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PHP+SQL4.

File handling basicsFile-based "database"File-based guestbook

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Guestbook structure• Guestbook form gb_form.html• Guestbook entries gb_entries.txt• Guestbook program guestbook.php

• From now on, we ALWAYS open the PHP file, the other files are managed by the PHP script

• After data modification/insertion, auto-redirect:header("location: guestbook.php");die();

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File format• Data fields: name, email, multi-line text

• To define data fields: we use prefix characters

#name1@email1entrytext1#name2@email2entrytext2

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Algorithm

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$_GET['action']ADD

ANYTHING ELSE

ENTRIES + LINK(???)

HTML(file_get_contents)

FORM

POST data? YES

NO

ERROR(echo)

SAVE(???)

REDIRECT(header + exit)

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Sub-parts of the exercise

1. gb_form.html: an html form with two single-line textbox (name, email), one multiline textbox (textarea: entry text) and one submit button

2. guestbook.php: according to the algorithm on the previous slide

3. Write the difficult parts:a) Display entriesb) Save entries

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Display entriesOpen fileIf success, then LOOP, while (not EOF)

Read line, determine first characterIf '#', then start new entry, echo nameIf '@', then echo email addressOtherwise, echo line without modification

LOOP endsDisplay html link towards the "New entry" action

(guestbook.php?action=FORM)

• Instead of line-by-line operations, we could use file(), but we usually need FILE_IGNORE_NEW_LINES

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Save entryCheck Name, Email, Entry in $_POST-banImport Name, Email, Entry from $_POSTOpen file for appendAppend "#" + name + newlineAppend "@" + email + newlineAppend entry + newlineClose file

??? What if the entry's first character is # or @ ?????? XSS: htmlspecialchars/strip_tags ???

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LET'S CODE!

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