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PHP class notes-unit 4, Lecture notes of Programming Languages

PHP class notes-unit 4 syllabus: File Handling, working with databases, Session, cookie and FTP.

Typology: Lecture notes

2018/2019

Uploaded on 08/12/2019

krishnavalli-singaravelan
krishnavalli-singaravelan 🇮🇳

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Contents
File Handling..................................................................................................................................................... 3
Opening les..................................................................................................................................................... 3
feof () & fgets()..................................................................................................................................................... 4
Closing a le..................................................................................................................................................... 4
Reading from a le character by character.............................................................................................................. 4
Reading a whole le at once.................................................................................................................................... 5
Reading a File into an Array..................................................................................................................................... 5
Checking if the les exist......................................................................................................................................... 6
Geng le Size..................................................................................................................................................... 6
Reading Binary Files.................................................................................................................................................7
Parsing les..................................................................................................................................................... 7
Parsing ini les..................................................................................................................................................... 8
Geng le info..................................................................................................................................................... 8
Stats ():..................................................................................................................................................... 8
Seng the le pointer locaon............................................................................................................................... 9
Copying Files..................................................................................................................................................... 9
Deleng Files..................................................................................................................................................... 10
Working with Databases............................................................................................................................................ 10
Php with Databases............................................................................................................................................... 10
MySQL..................................................................................................................................................... 10
Accessing Database through PHP.......................................................................................................................... 12
Steps to Connect to database............................................................................................................................ 12
Updang Databases........................................................................................................................................... 14
Insert into Database...........................................................................................................................................15
Deleng Records................................................................................................................................................ 15
Creang New Table............................................................................................................................................15
Creang new Database...................................................................................................................................... 16
Sorng the Database......................................................................................................................................... 16
Session, Cookies & FTP.............................................................................................................................................. 17
Cookie..................................................................................................................................................... 17
Reading a Cookie............................................................................................................................................... 18
Seng Expiraon Time...................................................................................................................................... 18
Deleng a Cookie...............................................................................................................................................18
FTP..................................................................................................................................................... 18
Connecng to a FTP server.................................................................................................................................... 19
To get a directory lisng.........................................................................................................................................19
Downloading les with FTP....................................................................................................................................19
Uploading Files with FTP........................................................................................................................................20
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Contents

  • File Handling.....................................................................................................................................................
    • Opening files.....................................................................................................................................................
    • feof () & fgets().....................................................................................................................................................
    • Closing a file.....................................................................................................................................................
    • Reading from a file character by character..............................................................................................................
    • Reading a whole file at once....................................................................................................................................
    • Reading a File into an Array.....................................................................................................................................
    • Checking if the files exist.........................................................................................................................................
    • Ge�ng file Size.....................................................................................................................................................
    • Reading Binary Files.................................................................................................................................................
    • Parsing files.....................................................................................................................................................
    • Parsing ini files.....................................................................................................................................................
    • Ge�ng file info.....................................................................................................................................................
      • Stats ():.....................................................................................................................................................
    • Se�ng the file pointer loca�on...............................................................................................................................
    • Copying Files.....................................................................................................................................................
    • Dele�ng Files.....................................................................................................................................................
  • Working with Databases............................................................................................................................................
    • Php with Databases...............................................................................................................................................
    • MySQL.....................................................................................................................................................
    • Accessing Database through PHP..........................................................................................................................
      • Steps to Connect to database............................................................................................................................
      • Upda�ng Databases...........................................................................................................................................
      • Insert into Database...........................................................................................................................................
      • Dele�ng Records................................................................................................................................................
      • Crea�ng New Table............................................................................................................................................
      • Crea�ng new Database......................................................................................................................................
      • Sor�ng the Database.........................................................................................................................................
  • Session, Cookies & FTP..............................................................................................................................................
    • Cookie.....................................................................................................................................................
      • Reading a Cookie...............................................................................................................................................
      • Se�ng Expira�on Time......................................................................................................................................
      • Dele�ng a Cookie...............................................................................................................................................
  • FTP.....................................................................................................................................................
    • Connec�ng to a FTP server....................................................................................................................................
    • To get a directory lis�ng.........................................................................................................................................
    • Downloading files with FTP....................................................................................................................................
    • Uploading Files with FTP........................................................................................................................................
    • Delete a file with FTP.............................................................................................................................................
    • Crea�ng Removing Directories with FTP................................................................................................................
    • Sending E-Mail.....................................................................................................................................................
  • Sessions.....................................................................................................................................................
    • Wri�ng a hit counter using Session.......................................................................................................................
    • Difference between Session & Cookie...................................................................................................................

$handle = fopen(“/home/file.txt” , “r”); $handle variable can be now used to work with the file.

  • To open a file for binary writing, $h = fopen(“/home/file.txt” , ”wb”);
  • Backslashes () can also be used in file path. In such case, they should be escaped by a (\) double backslash.
  • In the file location, the files in other websites can also be used, if given the complete address of the file. E.g: Program 4. <? php $h = fopen(“file.txt”, “r”); if ($h) echo “file opened OK”;’ ?>

▲ In the above program,

  • the file “file.txt” is opened in read mode.
  • after opening file, if successful fopen will return TRUE.
  • the message is displayed if fopen is successful. E.g.: $h = fopen (http://www.php.net , “r”); This will open the URL on the internet, preparing to read from web pages.

feof () & fgets()

  • feof() function gets the file handle as argument and will return TRUE if end of file is reached.
  • Syntax: feof()
  • feof() is usually added to a conditional statement.
  • fgets() will read a string of text from the file.
  • Syntax: fgets( [,length])
  • fgets() gets the file handle as argument, with an optional argument ‘length’ of the string to read.
  • fgets() reads (length-1) bytes from the file.
  • The default length is 1024 bytes. E.g.: Program 4. <?php

$h = fopen("file.txt" , "r"); while (!feof($h)) { $text = fgets($h); echo $text, "
"; } ?>

  • In the above program,
    • $h is the handle for the file “file.txt” which is opened in read only mode.
    • The file pointer moves through the file and copies the text to $text variable till end of file is reached.
    • The data is then displayed on screen.

Closing a file

  • Every file that is opened should be closed.
  • Closing a file frees up the resources connected with the file.
  • Properly closes the file.
  • Syntax: fclose(<$file handle>);
  • This function returns true if the file is successfully closed.
  • E.g.: Program 4. <?php $h = fopen("file.txt" , "r"); while (!feof($h)) { $t = fgets($h); echo $t; } fclose ($h); ?> The above program,
  • Fopen a file using fopen() function.
  • Reads string using fgets()
  • Finally closes the file handle using fclose().

offset - offset into the file at which to start reading. maxlen - maximum length of the data to read.

  • Except the filename option, the remaining arguments are optional.
  • In the file name argument, either the name of the file with its path or the address of a website is include.
  • E.g.: Program 4. <?php $te = file_get_contents("file.txt"); $f_t = str_replace("\n", "
    " , $te); echo $f_t; ?>
  • In the above program.
    • $te variable holds the entire contents of the file “file.txt”.
    • In the next line, the \n character in the file is replaced with
      tag.
    • The file content is then displayed.
  • To move a whole website, the address of the page is passed as parameter.

Reading a File into an Array

  • Storing the entire file into an array is achieved using the function file( ).
  • Syntax: file(filename [, use_include_path [, context]])
  • filename – name of the file to open.
  • The function returns an array or FALSE if failed.
  • Each line of the document becomes an element of the array.
  • This is useful to fetch data’s in a binary database.
  • E.g.: File.txt:

Aa bb cc dd

Php program: Program 4.

$ln) echo "Line $no: $ln
"; ?>
  • In the above program,
  • The text in “file.txt” is stored in array $dt.
  • The stored array is then displayed one by one.
  • The file has 3 lines therefore the array will have 3 elements.
  • Each array element will have a \n character in the end.
  • To get rid of the new line, rtrim () function is used.

Checking if the files exist

  • To check if the file already exist in the computer, file_exist ( ) function is used.
  • The file to be searched is passed as argument.
  • The function will return TRUE if the file exists and a FALSE otherwise.
  • Syntax: file_exists (filename)
  • The file name is passed as argument and the function will return TRUE if the file exist, otherwise FALSE is returned.
  • E.g.: Program 4. <?php $fnm = "temp.txt"; if (file_exists($fnm)) { $data = file($fnm); foreach ($dt as $no => $line) { echo "Line $no:", $line, "
    "; } }
  • In the above program,
    • The file “file.txt” is opened in “rb” mode.
    • To the fread function, the handle and the size of the file is passed.
    • fread function returns the whole content of the file into the variable $text.
    • The “\n” is then replaced with
      tag.
    • The same text is then displayed on screen.
    • Finally the handle is closed.
    • The output will be the contents of the file “file.txt”.

Parsing files

  • The binary files can be parsed using function fscanf ().
  • Syntax: fscanf ($handle, format)
  • The function takes a file handle and format as arguments
  • Format string is same as is used for other printf function.
  • E.g.: Program 4. <?php $h = fopen("actors.txt" , "r"); while ($n = fscanf($h, "%s\t %s\n")) { list ($f_name, $l_name) = $n; echo $f_name, " ", $l_name, "
    "; } fclose($h); ?> - In the above program,
    • actors.txt is a formatted file which is already available.
    • The data’s in actors.txt is in a format (String, tab space, String, new line).
    • A similar format is given to the format of fscanf function
    • The fetched data is splitted, into 2 variables and displayed separately.
    • The contents of “Actors.txt” is

Jim Carry Bob Miller Bryan Grant.

  • The records are arranged in a predefined format, such a file is termed as Binary File.
  • fread() function will return the entire data’s as one string.
  • Whereas scanf() function will expect the data’s in the prescribed format and the return value is stored in a single variable.

Parsing ini files

  • Parse_ini_files() is a function that is used to read ini files.
  • Syntax: Parse_ini_file(filename [, process section])
  • This function loads in the ini file and returns the setting in an associative array.
  • A TRUE in process section argument will allow multidimensional array with the sections & settings; default value is FALSE.
  • E.g.: Program 4. Sample.ini ; This is a sample ini file

[First section] first_color = red second_color = while third_color = blue

[Second section] File= “/usr/local/code.data” URL = http://www.php.net

  • Program to read and parse this ini file is: <?php $arr = parse_ini_file("sample.ini"); foreach ($arr as $key => $val) { echo "$key ----------- $val
    ";
  • The elements of the array can be accessed using the numeric index or the string index.
  • For numeric index the size of the file will be in $arr [7].

Setting the file pointer location

  • The file pointer points to the current location in the file.
  • When a file is opened, the pointer is set to the first location.
  • fseek() function is used to a move the file pointer location to desired location.
  • Syntax: fseek (handle, offset, [start_point]);

handle - handle of thee referenced file. offset - no. of bytes to set the pointer to. start point - starting point for the pointer.

  • Starting point is optional. It can be any one of the following constants.
    • SEEK_SET : Beginning of file.
    • SEEK_CUR : Current pointer location.
    • SEEK_END : End of the file
  • Offset can be a +ve or –ve number.

Copying Files

  • To copy the content of one file to another file, copy( ) function is used.
  • Syntax: copy(source, destination);
  • This function returns TRUE if the copy was successful.
  • E.g.: Program 4. <?php $s = 'file.txt'; $d = 'copy.txt'; if (!file_exists($d)) { if (copy($s, $d)) echo "Copy Successful"; } else

echo "could not copy $s
File already exists"; ?>

Deleting Files

  • To delete a file entirely, unlink( ) function is used.
  • Syntax:

unlink(filename [,context]) filename – filename to be deleted.

  • This function returns TRUE if the delete was successful.
  • E.g.: Program 4. <?php if (unlink("copy.txt")) echo "Deleted the file"; else echo "could not delete file"; ?> - In the above program,
    • The file “copy.txt” is deleted from disk using unlink( ) function.
    • The deleted operation is included in a condition.
    • Depending on the condition is TRUE a message is displayed correspondingly.

Working with Databases

  • A Database is a collection of one or more tables.
  • Databases organize data for easy access and use by programs.
  • A common database construct is a table.
  • A table is a collection of data in rows and columns.
  • Each row in a table is called a record.
  • Each column in a record is called a field.

Php with Databases

  • Php handles databases on the server.
  • Php supports various kinds of database servers.

CREATE DATABASE ; This command will create an empty database. E.g.: CREATE DATABASE produce;

4. To view the list of available databases:

SHOW DATABASES;

5. To set a database as default database:

USE ; This will set the database mentioned as default databases. E.g.: USE produce;

6. Create new table:

CREATE TABLE

(field nm data type…); The above command will create a table table name with the fields added to it. E.g.: CREATE TABLE fruit (name VARCHAR (20), number VARCHAR (20));

  • The various data types used frequently are:

1. VARCHAR (length) - creates a variable length string.

2. INT - creates an integer.

3. DECIMAL (total digits, total places) - creates a decimal value.

4. DATETIME - creates a data and time object like 2008 – 11 – 15 20:00:00.

7. To show the list of tables in the current database:

SHOW TABLES;

This will display all the table names in the current databases.

8. To display the structure of a table,

DESCRIBE

; E.g.: DESCRIBE fruit; The above E.g. will display the structure of the table fruit.

9. To add DATA INTO DATABASES:

INSERT INTO

VALUES (value(s)); E.g.: INSERT INTO fruit VALUES (‘apple’, ‘1020’);

  • The above e.g. will add a record to the table.
  • Similarly any number of records can be added to a table.

10. To display the contents of a table:

SELECT * FROM

; E.g.: SELECT * FROM fruits: This above E.g. will display the entire contents of the table fruits.

11. To exit mysql monitor:

QUIT

Accessing Database through PHP

  • Php has many inbuilt function to interact with MySQL.
  • The function are:

mysql_affected_rows Get the number of rows affected by the previous

MySQL opera�on.

mysql_change_user Change the logged-in user.

mysql_data_seek Sek data in the database

mysql_drop_db Drop a MySQL database

mysql_fetch_array Fetch a result row as an associa�ve array, a numeric

array or both.

mysql_fetch_assoc Fetch a result row as an associa�ve array

mysql_field_len Return the length of a given field.

mysql_get_server_info Get MySQL server info.

mysql_info Get informa�on about the most recent query.

mysql_list_tables Lists the tables in a MySQL database.

mysql_list_fields Lists MySQL table fields.

mysql_result Get result data.

Steps to Connect to database

The examples in this book will work with PHP4 & 5.(Note: These are from the syllabus ) Whereas if you have installed PHP 7, which is the current version, the alternate commands are in the blog page, h�p:// viid.me/qr731T which is part of h�p://krishnas-php-tutorial.blogspot.in/

1. Connecting to database Server:

  • Php connects to databases using connection object.
  • To create connection object,
  • E.g.: $q = “select * from fruits”; $res = mysql_query ($q) or die (“query failed:”. mysql_error( ));
  • The sql query is stored in a variable separately for simplicity.
  • The variable is passed to mysql_query() function as parameter and the result is stored in variable $res.
  • At the end the variable will have data if query was successful or message with error string if failed.
  • The returned data has to be displayed with additional functions.

4. Displaying Table Data:

  • To extract individual rows from the return data, mysql_fetch_array( ) function is used.
  • This function returns an array corresponding to the current record in the data table.
  • Syntax: mysql_fetch_array (return [, result_type]) - result - resource returned by mysql_query function. - result_type - type of preferred array.
  • It can be either one of these: MYSQL_ASSOC, MYSQL_NUM MYSQL_BOTH is the default value. E.g.: while ($row = mysql_fetch_array($result)) { echo “
”; echo “”; echo “”; } The first statement assigns the current row from fruit table to $row.

Name field can be accessed like this: $row [‘name’] or $row [‘number’]

5. Closing connection object:

  • The connection to the database is closed using function mysql_close( ).
    • Syntax: mysql_close([link identifier]) where - link_idenifier: the connection object.
    • (^) E.g.: mysql_close($conn);

Example program to fetch data from database and display it. Program 4-

“, $row[‘name’], “ “, $row[‘number’], ”
”; echo “”; echo “”; echo “”; while ($r = mysql_fetch_array($res)) { echo “”; echo “”; echo “”; } echo “
Name Number
“, $row[‘name’], “ ” $row[‘number’], ”
”; mysql_close($conn);