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V 1.0 OE NIK 2013 PHP+SQL 4. File handling basics File-based "database" File-based guestbook 1.

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Presentation on theme: "V 1.0 OE NIK 2013 PHP+SQL 4. File handling basics File-based "database" File-based guestbook 1."— Presentation transcript:

1 V 1.0 OE NIK 2013 PHP+SQL 4. File handling basics File-based "database" File-based guestbook 1

2 V 1.0 OE NIK 2013 PHP+SQL 4. File handling basics File-based "database" File-based guestbook 2

3 V 1.0 Basic principles File paths: document_root ( ) vs php 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? OE NIK

4 V 1.0 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); OE NIK

5 V 1.0 Usage of files (one row contents) OE NIK

6 V 1.0 File modes ModesDescription rRead only. Starts at the beginning of the file r+Read/Write. Starts at the beginning of the file wWrite 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 aAppend. 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 xWrite 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 OE NIK

7 V 1.0 Perfect use OE NIK

8 V 1.0 WRONG use $file = fopen("welcome.txt", "r"); while(!feof($file)) { //Endless infinite loop!!!!!! echo fgets($file)." "; } fclose($file); Alternative solution: $file = fopen("welcome.txt", "r") or die("Unable to open file!"); OE NIK

9 V 1.0 Example: DOWNLOAD.PHP OE NIK

10 V 1.0 OE NIK 2013 PHP+SQL 4. File handling basics File-based "database" File-based guestbook 10

11 V 1.0 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) ) OE NIK

12 V 1.0 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 … … OE NIK

13 V 1.0 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 13 OE NIK 2013

14 V 1.0 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 14 OE NIK 2013

15 V 1.0 HOMEWORK (FOR POINTS!!!) Deadline: 17 th of March, midnight! to the subject must contain the letters [PHP], the text must contain your name and your neptun code The 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! ) 15 OE NIK 2013

16 V 1.0 OE NIK 2013 PHP+SQL 4. File handling basics File-based "database" File-based guestbook 16

17 V 1.0 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(); OE NIK

18 V 1.0 File format Data fields: name, , multi-line text To define data fields: we use prefix characters entry text 1 entry text 2 OE NIK

19 V 1.0 Algorithm OE NIK 2013 $_GET['action'] ADD ANYTHING ELSE ENTRIES + LINK (???) HTML (file_get_contents) FORM POST data? YES NO ERROR (echo) SAVE (???) REDIRECT (header + exit) 19

20 V 1.0 Sub-parts of the exercise 1.gb_form.html: an html form with two single-line textbox (name, ), 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 entries b)Save entries OE NIK

21 V 1.0 Display entries Open file If success, then LOOP, while (not EOF) Read line, determine first character If '#', then start new entry, echo name If then echo address Otherwise, echo line without modification LOOP ends Display 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 OE NIK

22 V 1.0 Save entry Check Name, , Entry in $_POST-ban Import Name, , Entry from $_POST Open file for append Append "#" + name + newline Append + + newline Append entry + newline Close file ??? What if the entry's first character is # ??? ??? XSS: htmlspecialchars/strip_tags ??? OE NIK

23 V 1.0 OE NIK 2013 LET'S CODE! 23

24 V 1.0 OE NIK

25 OE NIK


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