Htmlentities() converts all applicable characters to HTML entities. While htmlspecialcharacter()converts special characters to HTML entities. This means htmlentities( ) will check for non English language characters, such as French accents, the German umlaut, etc.

Copy() makes a copy of the file. It returns TRUE on success. It can copy from any source to destination. Move simply Moves the file to destination if the file is valid. While move can move the uploaded file from temp server location to any destination on the server. If filename is a valid upload file, but cannot be moved for some reason, no action will occur.

Opendir():- It opens the directory. This function returns a directory stream on success and FALSE and an error on failure.

Syntax:

Opendir(directory, context)

Context is a set of options that can modify the behavior of a stream

Example: opens sample directory.

$dir = opendir("directory");

Readdir(): It returns an entry from a directory handle opened by opendir().

Syntax:

Readdir(dir_stream)

Example:

$file = readdir($dir);

closedir(): It closes a directory handle opened by opendir().

Syntax:

closedir(dir_stream)

Example:

$file = close($dir);

Chmod() is used for changing permissions on a file.

Syntax:

Chmod(file, mode)

Mode here specifies the permissions as follows:

The first number is always zero

The second number specifies permissions for the owner

The third number specifies permissions for the owner's user group

The fourth number specifies permissions for everybody else

Possible values (to set multiple permissions, add up the following numbers)

1 = execute permissions

2 = write permissions

4 = read permissions

Example:

// everything for owner, read for owner's group

chmod("test.txt",0740);

Both GET and POST are used to collect data from a form. However, when security is desired $_POST should be used. When the $_ POST variable is used, all variables used are NOT displayed in the URL. Also, they have no restrictions to the length of the variables. GET should be used when the interaction with the form is more like a question. For e.g. firing a query etc. POST should be used more often when the interaction is more like an order or the interaction changes the state of the resource.

POST example:

<form action="sample.php" method="post">

Name: <input type="text" name="name" />

Age: <input type="text" name="age" />

<input type="submit" />

</form>

On clicking submit the URL resembles to: https://www.mysamplesite.com/sample.php

The sample.php file can be used for catching the form data using $_POST 

Hello <?php echo $_POST["name"]; ?>.<br />

You are <?php echo $_POST["age"]; ?> years old!

GET EXAMPLE

<form action="sample.php" method="get">

Name: <input type="text" name="name" />

Age: <input type="text" name="age" />

<input type="submit" />

</form>

On clicking submit the URL resembles to : https://www.mysamplesite.com/sample.php?name=jim&age=37

The sample.php file can be used for catching the form data using $_GET 

Hello <?php echo $_GET["name"]; ?>.<br />

You are <?php echo $_GET["age"]; ?> years old!

PHP supports single level inheritance.

Inheriting a class would mean creating a new class with all functionality of the existing class in addition to some more. The created class is called as a subclass of the parent class. Parent is a keyword which we use to access members of a parent class. Inheritance is usually defined by using the keyword “Extend”. $this is used a reference to the calling object. Inheritance avoids redundancy of code.

Example:

Class employee extends manager : Here Employee is a subclass of manager.

Echo $this->name can be used to echo variable name of the parent class.

Generating random passwords in PHP can be done in multiple ways depending on how much security the application demands:-

Md5 function can be passed one parameter as uniqid() function which in turn generates a random number. Passing the parameter as TRUE in uniqid() adds additional uniqueness.

<?php
   $passwd = md5(uniqid(rand(), true));
   Echo $passwd;
?>

A HTML form should be build before uploading the file. The following HTML code is used for selecting the file that is to be uploaded. The type attribute of input must be “file”.

<form enctype="multipart/form-data" action="uploader.php" method="POST">

<input type="hidden" name="MAX_FILE_SIZE" value="100000" />

Choose a file to upload: <input name="uploadedfile" type="file" /><br />

<input type="submit" value="Upload File" />

</form>

At the time of executing uploader.php, the uploaded file will be stored in a temporary storage are on the webserver. An associative array $_FILES['uploadedfile']['name'] is used for uploading. The ‘name’ is the original file that is to be uploaded. Another associative array $_FILES['uploadedfile']['tmp_name'] is used for placing the uploaded file in a temporary location on the server and the file should be empty and should exist with the tmp_name.

The following code snippet is used for uploading the file.

$target_path = "uploads/"; // the target location of the file

$target_path = $target_path . basename( $_FILES['uploadedfile']['name']);

if(move_uploaded_file($_FILES['uploadedfile']['tmp_name'], $target_path)) 

{

       echo "The file ". basename( $_FILES['uploadedfile']['name']). 

        " has been uploaded";

}

else

{

      echo “There was an error while uploading the file”;

}

The function move_uploaded_file()is used to place the source file into the destination folder, which resides on the server.

If the uploading is successful, the message “The file filename has been uploaded. Otherwise the error message “There was an error while uploading the file” would be displayed.