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.

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);

User names and passwords in PHP can be encrypted using md5 function.

MD5 function calculates the md5 hash of a string. It is basically used for encryption. It is also used for digital signature applications, where a large file must be "compressed" in a secure manner.

Example:

Md5($str);

Crypt() function can also be used to encrypt a string,. It used MD5, DES or blow fish algorithms for encryption.

Syntax:

Crypt(str, salt)

Salt is an optional parameter used to increase the number of characters encoded, to make the encoding more secure

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;
?>

To pass the information into the script from outside, help can be taken from the PHP CLI (Command line interface) method. Suppose addition of two numbers has to be passed to PHP then it can be passed like this on the command line:

php add.php 2 3

Here the script name is add.php, and 2 and 3 are the numbers that has to be added by the script. These numbers are available inside the script in an array called $argv. This array contains all the information on the command line; the statement is stored as follows:

$argv[0]=add.php

$argv[1]=2

$argv[2]=3

So, $argv always contains at least one element — the script name.

Then, in your script, you can use the following statements:

$sum = $argv[1] + $argv[2];

echo $sum;

$argc is a variable that stores the numbers of elements in $argv. $argc is equal to at least 1, which is saved for the name of the script. Example is $argc=3 using the above statements.

$_SERVER and $_ENV arrays contain different information. The information depends on the server and operating system being used. Most of the information can be seen of an array for a particular server and operating system. The syntax is as follows:

foreach($_SERVER as $key =>$value)

{ echo “Key=$key, Value=$value\n”; }

The difference lies with the execution of the languages. PHP is server side scripting language, which means that it can’t interact directly with the user. Whereas, JavaScript is client side scripting language, that is used to interact directly with the user.