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III BCOM(CA)-UNIT-IV


unit-4




Q) How to include files in PHP documents.
Include statement enables to incorporate other files (usually other PHP scripts) into PHP documents. The include (or require) statement takes all the text/code/markup that exists in the specified file and copies it into the file that uses the include statement.

Syntax:
include 'filename';
or
require 'filename';
Example:
footer.php
<?php
echo "<p>Welcome to my Website</p>";
?>

Xyz.php
<html><body>
<h1>Welcome to my home page!</h1>
<p>Some text.</p>
<p>Some more text.</p>
<?php
include 'footer.php';
?>
</body>
</html>

The include statement can be used with control structures such as conditional statements and looping statements.

Example-conditional statement:
$test = “1”;
if ($test == “2”) {
include ‘file.txt’; // won’t be included
}

Example-looping statement:
<?php
 for ($x = 1; $x<=3; $x++) {
 $incfile = “incfile”.$x.”.txt”;
echo “Attempting to include “.$incfile.”<br/>”;
include $incfile;
echo “<hr/>”;
}
?>

Q) How to move files from one server to another server
When project move to a new server, we have to change a hundred or more include paths, if this is hard-coded in a hundred or more files. we can escape this fate by setting the include_path directive in php.ini file:

include_path .:/home/user/bob/htdocs/project4/lib/

The include_path value can include as many directories as you want, separated by colons (semicolons in Windows). The order of the items in the include_path directive determines the order in which the directories are searched for the named file. The first dot (.) before the first colon indicates “current directory,” and should be present.

Q) How to Validate Files in PHP.

PHP provides many functions to help to discover information about files. Such as
1)    Checking for existing of a file.
2)    Checking whether it is a file or a directory
3)    Checking status of a file.
4)    Checking the size of a file

1.    Checking for Existence:  The existence of a file can be test with the file_exists() function. This function requires a string representation of an absolute or relative path to a file, which might or might not be present. If the file is found, the file_exists() function returns true; otherwise, it returns false.

Example:
if (file_exists(‘test.txt’)) {
echo “The file exists!”;
}

2.    A file or a Directory?: is_file( ) and is_dir ( ): To check whether it is a file or director we use is_file and is_dir () functions. The is_file() function requires the file path and returns a Boolean value and the is_dir() requires the path to the directory and returns a Boolean value.
Example:
if (is_file(‘test.txt’)) {
echo “test.txt is a file!”;
}
if (is_dir(‘/tmp’)) {
echo “/tmp is a directory”;
}

3.   Checking the Status of a File:
1)    The is_readable() function tells whether it can read a file or not. The is_readable() function accepts the file path as a string and returns a Boolean value:
Example:
if (is_readable(‘test.txt’)) {
echo “test.txt is readable”;
}
2)    The is_writable( ) function tells about the proper permission to write to a file. As with is_readable(), the is_writable() function requires the file path and returns a Boolean value.
Example:
if (is_writable(‘test.txt’)) {
echo “test.txt is writable”;
}
3)    The is_executable( ) function tells whether it can execute the given file,relying on either the file’s permissions or its extension, depending on platform. The function accepts the file path and returns a Boolean value.
Example:
if (is_executable(‘test.txt’)) {
echo “test.txt is executable”;
}

4.    Determining File Size: The filesize() function attempts to determine and return its size in bytes. It returns false if it encounters problems:
Example:
echo “The size of test.txt is “.filesize(‘test.txt’);

Q) How to creating and deleting files in PHP.

Creating a FILE: The touch( ) function is used to create a file. A string in touch () function, represents a file name. If the file already exists, its contents is not disturbed, but the modification date is updated to reflect the time at which the function executed:

touch(‘myfile.txt’);

Deleting a FILE: we can delete or remove an existing file with the unlink() function. unlink() accepts a file path:

unlink(‘myfile.txt’);


Q) What are the different types of Opening modes of a File for Writing, Reading, or Appending.
Opening a FILE: PHP provides the fopen() function to open a file and this function requires a string that contains the file path, followed by a string that contains the mode in which the file is to be opened. The most common modes are read (r), write (w), and append (a).

The following code is used to open a file for reading:

$fp = fopen(“test.txt”, “r”);

The following code is used to to open a file for writing:

$fp = fopen(“test.txt”, “w”);

The following code is used  to open a file for appending (that is, to add data to the end of a file):

$fp = fopen(“test.txt”, “a”);

closing a file: using fclose() we can close the file.

fclose($fp);


Q) Explain how to read data from files in PHP.

PHP provides a number of functions for reading data from files. These functions enable to read by the byte, by the whole line, and even by the single character.
1.   fgets() and feof():
fgets(): The fgets() function  is used to read a line from an open file. The fgets() function reads the file until it reaches a newline character (“/n”), the number of bytes specified in the length argument, or the end of the file—whichever comes first:

In fgets() function we can pass an integer as a second argument, which specifies the number of bytes that the function should read if it doesn’t first encounter a line end or the end of the file.

$line = fgets($fp, 1024);

feof(): The feof() function is used to tell that it reaches to the end of the file. The feof() function does this by returning true when the end of the file has been reached and false otherwise.

Example:    feof($fp);

2.    fread(): Rather than reading text by the line, we can read a file in arbitrarily defined chunks. The fread() function accepts a file resource as an argument, as well as the number of bytes want to read. The fread() function returns the amount of data requested, unless the end of the file is reached first.
Example:
$chunk = fread($fp, 8);
3.    fgetc(): The fgetc() function is similar to fgets() except that it returns only a single character from a file every time it is called. Because a character is always 1 byte in size, fgetc() doesn’t require a length argument.
Example:
$char = fgetc($fp);

4.   file_get_contents( ): using file_get_contents() to read an entire file into a string.
Example:
$contents = file_get_contents(“test.txt”);

Q) Explain briefly about Writing or Appending to a FILE.

The processes for writing to and appending to a file are the same—the difference lies in the mode with which it call the fopen() function.
When it write to a file,it use the mode argument “w”.

$fp = fopen(“test.txt”, “w”);

All subsequent writing occurs from the start of the file. If the file doesn’t already exist, it is created. If the file already exists, any prior content is destroyed and replaced by the data to write.
When it append to a file, it use the mode argument “a”.

$fp = fopen(“test.txt”, “a”);

Any subsequent writes to file are added to the end of existing content, but if it attempt to append content to a nonexistent file, the file is created first.

Writing to a File with fwrite() or fputs()
The fwrite() function accepts a file resource and a string, and then writes the string to the file. The fputs() function works in exactly the same way:

fwrite($fp, “hello world”);
fputs($fp, “hello world”);


<?php
 $filename = “test.txt”;
echo “<p>Writing to “.$filename.” ... </p>”;
 $fp = fopen($filename, “w”) or die(“Couldn’t open $filename”);
 fwrite($fp, “Hello world\n”);
 fclose($fp);
 echo “<p>Appending to “.$filename.” ...</p>”;
 $fp = fopen($filename, “a”) or die(“Couldn’t open $filename”);
 fputs($fp, “And another thing\n”);
 fclose($fp);
 ?>

Q) Explain working with directories.

PHP provides many functions for working with directories.
1.    mkdir(): The mkdir() function enables to create a directory. The mkdir() function requires a string that represents the path to the directory to create and an octal number integer that represents the mode to set for the directory.

The mode argument has an effect only on UNIX systems. The mode should consist of three numbers between 0 and 7, representing permissions for the directory owner, group, and everyone, respectively.

Example:

mkdir(“testdir”, 0777); // global read/write/execute permissions
mkdir(“testdir”, 0755); // world/group: read/execute; owner: read/write/execute

2.    rmdir(): The rmdir() function enables to remove a directory from the filesystem. The rmdir() function requires only a string representing the path to the directory to delete.
Example:
rmdir(“testdir”);

3.    opendir():  The opendir() function requires a string that represents the path to the directory to open. The opendir() function returns a directory handle unless the directory isn’t present or readable; in that case, it returns false:
Example:
$dh = opendir(“testdir”);

In this case, $dh is the directory handle of the open directory.

4.   readdir(): The readdir() function requires a directory handle and returns a string containing the item name. If the end of the directory is reached, readdir() returns false.

Note that readdir() returns only the names of its items, rather than full paths.

Q) Explain Opening Pipes to and from Processes Using popen()
We can open a pipe to a process using the popen() function. The popen() function is used like this:

$file_pointer = popen(“some command”, mode)

The mode is either r (read) or w (write).

Example:
<?php
$file_handle = popen(“/path/to/fakefile 2>&1”, “r”);
$read = fread($file_handle, 2096);
echo $read;
pclose($file_handle);
?>
Q) Explain the following Running Commands
a) exec( )
b) system() or passthru()
The exec() function is one of several functions use to pass commands to the shell. The exec() function requires a string representing the path to the command to run, and optionally accepts an array variable that will contain the output of the command and a scalar  variable that will contain the return value (1 or 0).
exec(“/path/to/somecommand”, $output_array, $return_val);
Example:
<?php
exec(“ls -al .”, $output_array, $return_val);
echo “Returned “.$return_val.”<br/><pre>”;
foreach ($output_array as $o) {
  echo $o.”\n”;
}
echo “</pre>”;
?>
The above program Using exec() and ls to Produce a Directory Listing
System():  The system() function is similar to the exec() function in that it launches an external application, and it utilizes a scalar variable for storing a return value:
system(“/path/to/somecommand”, $return_val);

The system() function differs from exec() in that it outputs information directly to the browser, without programmatic intervention.

The following snippet of code uses system() to print a man page for the man command, formatted with the <pre></pre> tag pair:

<?php
echo “<pre>”;
system(“man man | col –b”, $return_val);
echo “</pre>”;
?>
Q) Explain the Working with Images
PHP has many built-in functions for dynamically creating and manipulating images. Popular uses include the creation of charts and graphs and the modifications of existing images to display watermarks.
Understanding the Image-Creation Process
Creating an image with PHP is not like creating an image with a drawing program (for example, Sumo Paint, Corel DRAW, or Windows Draw): There’s no pointing and clicking or dragging buckets of color into a predefined space to fill image. Similarly, there’s no Save As functionality, in which drawing program automatically creates a GIF, JPEG, PNG, and so on.

Instead, we have to become the drawing application. As the programmer, you must tell the PHP engine what to do at each step along the way. You are responsible for using the individual PHP functions to define colors, draw and fill shapes, size and resize the image, and save the image as a specific file type.

Example:

<?php
$my_img = imagecreate( 200, 80 );
$background = imagecolorallocate( $my_img, 0, 0, 255 );
$text_colour = imagecolorallocate( $my_img, 255, 255, 0 );
$line_colour = imagecolorallocate( $my_img, 128, 255, 0 );
imagestring( $my_img, 4, 30, 25, "thesitewizard.com", $text_colour );
imagesetthickness ( $my_img, 5 );
imageline( $my_img, 30, 45, 165, 45, $line_colour );

header( "Content-type: image/png" );
imagepng( $my_img );
imagecolordeallocate( $line_color );
imagecolordeallocate( $text_color );
imagecolordeallocate( $background );
imagedestroy( $my_img );
?>


Q) How to Draw a new image.

Creating an image is a stepwise process and includes the use of several different PHP functions. Creating an image begins with the ImageCreate() function, but all this function does is set aside a canvas area for your new image. The following line creates a drawing area that is 300 pixels wide by 300 pixels high:

$myImage = ImageCreate(300,300);

With a canvas now defined, you should next define a few colors for use in that new image. The following examples define five such colors (black, white, red, green, and blue, respectively), using the ImageColorAllocate() function and RGB values:

$black = ImageColorAllocate($myImage, 0, 0, 0);
$white = ImageColorAllocate($myImage, 255, 255, 255);
$red  = ImageColorAllocate($myImage, 255, 0, 0);
$green = ImageColorAllocate($myImage, 0, 255, 0);
$blue = ImageColorAllocate($myImage, 0, 0, 255);

Drawing Shapes and Lines
Several PHP functions can assist you in drawing shapes and lines on your canvas:
·         ImageEllipse() is used to draw an ellipse.
·         ImageArc() is used to draw a partial ellipse.
·         ImagePolygon() is used to draw a polygon.
·         ImageRectangle() is used to draw a rectangle.
·         ImageLine() is used to draw a line.

Example:
?php
$myImage = ImageCreate(300,300);
  $black = ImageColorAllocate($myImage, 0, 0, 0);
  $white = ImageColorAllocate($myImage, 255, 255, 255);
  $red  = ImageColorAllocate($myImage, 255, 0, 0);
  $green = ImageColorAllocate($myImage, 0, 255, 0);
 $blue = ImageColorAllocate($myImage, 0, 0, 255);

 ImageRectangle($myImage, 15, 15, 95, 155, $red);
 ImageRectangle($myImage, 95, 155, 175, 295, $white);
 ImageRectangle($myImage, 175, 15, 255, 155, $red);

header (“Content-type: image/png”);
 ImagePng($myImage);

ImageDestroy($myImage);
 ?>

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