Question

In this research, you are asked to write about php programming language,

write a dummy paper to show all the required information about this language that might help readers with less knowledge to know how to use it. Use the following points to talk about your programming language:

- The historical background when, how this language began and, what is the domain that it was used for.
- The category of this language, according to Language categories in Chapter1.
- The primitive data types are available in the chosen language.

- The operator precedence rules and the associative rules.
- The rules of naming variables (Case sensitivity, keywords), Show examples. - Does the language support type checking?
- Write a set of code that shows how to implement:

* an array.
* a pointer/reference type.
* a union type.
* relation or Boolean expression.
* assignment statements: simple, unary, as an expression, and multiple. * a kind of Selection statement.
* one type of iterative statement.

include more information as much as you see, that is appropriate. Show your skills and knowledge on how to write a scientific paper. Include all required information such as your information, references, a decent introduction, and the look of the overall document. .

Answer 1

Introduction to PHP

A script is a set of programming instructions that is interpreted at runtime. A scripting language is a language that interprets scripts at runtime. Scripts are usually embedded into other software environments. The purpose of the scripts is usually to enhance the performance or perform routine tasks for an application.

Server side scripts are interpreted on the server while client side scripts are interpreted by the client application.

PHP is an acronym for "PHP: Hypertext Pre processor", PHP is a widely-used, open source scripting language. PHP scripts are executed on the server.

PHP is a server side scripting that is interpreted on the server while JavaScript is an example of a client side script that is interpreted by the client browser. Both PHP and JavaScript can be embedded into HTML pages.

Pre Requisites to learn PHP : HTML, CSS and JavaScript.

History of PHP

PHP was created in 1995 by Rasmus Lerdorf and means Personal Home Page language. Ever since its beginning it has been one of the most intuitive programming languages used for the creation of dynamic web pages. Later, when the PHP team was formed, the parser was rewritten and PHP version 3.0 saw the light of day. The PHP 3 version was the first serious improvement of the PHP language, which fixed a lot of bugs and completely redesigned the PHP core. The meaning of the abbreviation was also changed to PHP Hypertext Preprocessor.

Ever since its beginning PHP has been one of the most intuitive programming languages used for the creation of dynamic web pages. PHP comes under scripting language.

Why PHP?

PHP runs on various platforms (Windows, Linux, Unix, Mac OS X, etc.)

PHP is compatible with almost all servers used today (Apache, IIS, etc.)

PHP supports a wide range of databases

PHP is free to download and use.

PHP is easy to learn and runs efficiently on the server side.

Primitive datatypes in PHP

PHP supports the following 8 data types:

1. String
2. Integer
3. Float (floating point numbers - also called double)
4. Boolean
5. Array
6. Object
7. NULL
8. Resource

Operator Precedence and Associativity

Here operators with the highest precedence appear at the top of the table, those with the lowest appear at the bottom. Within an expression, higher precedence operators will be evaluated first.

Operator Precedence	Operator	Associativity
1. 1.Unary	! ++ --	Right to left
2. Multiplicative	* / %	Left to right
3. Additive	+ -	Left to right
4. Relational	< <= > >=	Left to right
5. Equality	== !=	Left to right
6. Logical AND	&&	Left to right
7. Logical OR	||	Left to right
8. Conditional	?:	Right to left
9. Assignment	= += -= *= /= %=	Right to left

Creating (Declaring) PHP Variables

In PHP, a variable starts with the $ sign, followed by the name of the variable:

Example:

<?php
$txt = "Hello world!";
$x = 5;
$y = 10.5;
?>

After the execution of the statements above, the variable $txt will hold the value Hello world!, the variable $x will hold the value 5, and the variable $y will hold the value 10.5.

PHP Variables

A variable can have a short name (like x and y) or a more descriptive name (age, carname, total_volume).

Rules for PHP variables:

• A variable starts with the $ sign, followed by the name of the variable
• A variable name must start with a letter or the underscore character
• A variable name cannot start with a number
• A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ )
• Variable names are case-sensitive ($age and $AGE are two different variables)

List of all PHP keywords

· abstract

· and

· Array()

· as

· break

· callable

· continue declare

· default

· die()

· do

· echo

· else

· elseif

· empty  

· enddeclare        

· endfor

· endforeach

· endif    

· endswitch

· endwhile            

· eval()   

· exit()    

· extends                              

· final      

· finally

· for

· foreach

· function

· global

· goto

· if

· implements

· include

· include_once

· instanceof

· insteadof

· interface

· isset()

· list()

· namespace()

· new

· or

· print

· private

· protected

· public

· require

· require_once

· return

· static

· switch

· throw

· trait

· try

· unset()

· use

· var

· while

· xor

· yield

· yield_form

PHP | gettype() Function

The gettype() function is an inbuilt function in PHP which is used to get the type of a variable. It is used to check the type of existing variable.

Syntax:

string gettype ( $var )

Parameter: This function accepts a single parameter $var. It is the name of variable which is needed to be checked for type of variable.

Example:

<?php // PHP program to illustrate gettype() function $var1 = true; // boolean value $var2 = 3; // integer value $var3 = 5.6; // double value $var4 = "Abc3462"; // string value $var5 = array(1, 2, 3); // array value $var6 = new stdClass; // object value $var7 = NULL; // null value $var8 = tmpfile(); // resource value echo gettype($var1)."\n"; echo gettype($var2)."\n"; echo gettype($var3)."\n"; echo gettype($var4)."\n"; echo gettype($var5)."\n"; echo gettype($var6)."\n"; echo gettype($var7)."\n"; echo gettype($var8)."\n";

Creating an Array in PHP

In PHP, the array() function is used to create an array:

array();

In PHP, there are three types of arrays:

• Indexed arrays - Arrays with a numeric index
• Associative arrays - Arrays with named keys
• Multidimensional arrays - Arrays containing one or more arrays

Get The Length of an Array - The count() Function

The count() function is used to return the length (the number of elements) of an array:

Example

<?php
$cars = array("Volvo", "BMW", "Toyota");
echo count($cars);
?>

Reference Types in PHP

References in PHP are a means to access the same variable content by different names. They are not like C pointers; for instance, you cannot perform pointer arithmetic using them, they are not actual memory addresses, and so on. Instead, they are symbol table aliases. Note that in PHP, variable name and variable content are different, so the same content can have different names. The closest analogy is with Unix filenames and files - variable names are directory entries, while variable content is the file itself

As said before, references are not pointers. That means, the following construct won't do what you expect:

<?php
function foo(&$var)
{
    $var =& $GLOBALS["baz"];
}
foo($bar);
?>

What happens is that $var in foo will be bound with $bar in the caller, but then re-bound with $GLOBALS["baz"]. There's no way to bind $bar in the calling scope to something else using the reference mechanism, since $bar is not available in the function foo (it is represented by $var, but $var has only variable contents and not name-to-value binding in the calling symbol table). You can use returning references to reference variables selected by the function.

Union in PHP

Ds\Set::union — Creates a new set using values from the current instance and another set

Example

public Ds\Set::union ( Ds\Set $set ) : Ds\Set

Creates a new set that contains the values of the current instance as well as the values of another set.

Logical / Boolean Operators in PHP

Operator	Name	Example	Result
and	And	$x and $y	True if both $x and $y are true
or	Or	$x or $y	True if either $x or $y is true
xor	Xor	$x xor $y	True if either $x or $y is true, but not both
&&	And	$x && $y	True if both $x and $y are true
||	Or	$x || $y	True if either $$x or $y is true
!	Not	!$x	True if $x is not true

The following example will show you these logical operators in action:

Example

Run this code »

 <?php

 $year = 2014;

 // Leap years are divisible by 400 or by 4 but not 100

 if(($year % 400 == 0) || (($year % 100 != 0) && ($year % 4 == 0))){

 echo "$year is a leap year.";

 } else{

 echo "$year is not a leap year.";

 }

 ?>

 PHP assignment operators

The PHP assignment operators are used with numeric values to write a value to a variable.

The basic assignment operator in PHP is "=". It means that the left operand gets set to the value of the assignment expression on the right.

x += y is same as x = x + y      i.e, Addition

x -= y is same as x = x – y       i.e, Subtraction

x *= y is same as x = x * y      i.e, Multiplicaction

x /= y is same as x = x / y        i.e, Division

x %= y is same as x = x % y    i.e, Modulus

 Example

 < !DOCTYPE html>

 <html>

 <body>

 <?php

 $x = 20;

 $x += 100;

 echo $x;

 ?>

 </body>

 </html>

PHP Selection/Conditional Statements

In PHP we have the following conditional statements:

• if statement - executes some code if one condition is true
• if...else statement - executes some code if a condition is true and another code if that condition is false
• if...elseif...else statement - executes different codes for more than two conditions
• switch statement - selects one of many blocks of code to be executed

Example

<?php
$t = date("H");

if ($t < "20") {
    echo "Have a good day!";
}
?>

<?php
$t = date("H");

if ($t < "20") {
echo "Have a good day!";
} else {
    echo "Have a good night!";
}
?>

<?php
$t = date("H");

if ($t < "10") {
    echo "Have a good morning!";
} elseif ($t < "20") {
    echo "Have a good day!";
} else {
    echo "Have a good night!";
}
?>

<?php
$favcolor = "red";

switch ($favcolor) {
    case "red":
        echo "Your favorite color is red!";
    break;
case "blue":
      echo "Your favorite color is blue!";
    break;
case "green":
      echo "Your favorite color is green!";
    break;
default:
      echo "Your favorite color is neither red, blue, nor green!";
}
?>

PHP Iterative statements/ Loops

Often when you write code, you want the same block of code to run over and over again a certain number of times. So, instead of adding several almost equal code-lines in a script, we can use loops.

Loops are used to execute the same block of code again and again, as long as a certain condition is true.

In PHP, we have the following loop types:

• while - loops through a block of code as long as the specified condition is true
• do...while - loops through a block of code once, and then repeats the loop as long as the specified condition is true
• for - loops through a block of code a specified number of times
• foreach - loops through a block of code for each element in an array

PHP while - loops

The while loop executes a block of code as long as the specified condition is true.

Syntax

while (condition is true) {
    code to be executed;
}

The example below displays the numbers from 1 to 5:

Example

<?php
$x = 1;

while($x <= 5) {
    echo "The number is: $x <br>";
    $x++;
}
?>

The PHP do...while Loop

The do...while loop will always execute the block of code once, it will then check the condition, and repeat the loop while the specified condition is true.

Syntax

do {
code to be executed;
} while (condition is true);

Examples

The example below first sets a variable $x to 1 ($x = 1). Then, the do while loop will write some output, and then increment the variable $x with 1. Then the condition is checked (is $x less than, or equal to 5?), and the loop will continue to run as long as $x is less than, or equal to 5:

<?php
$x = 1;

do {
    echo "The number is: $x <br>";
    $x++;
} while ($x <= 5);
?>

The PHP for Loop

The for loop is used when you know in advance how many times the script should run.

Syntax

for (init counter; test counter; increment counter) {
   code to be executed for each iteration;
}

Parameters:

• init counter: Initialize the loop counter value
• test counter: Evaluated for each loop iteration. If it evaluates to TRUE, the loop continues. If it evaluates to FALSE, the loop ends.
• increment counter: Increases the loop counter value

The example below displays the numbers from 0 to 10:

Example

<?php
for ($x = 0; $x <= 10; $x++) {
    echo "The number is: $x <br>";
}
?>

Example Explained

• $x = 0; - Initialize the loop counter ($x), and set the start value to 0
• $x <= 10; - Continue the loop as long as $x is less than or equal to 10
• $x++ - Increase the loop counter value by 1 for each iteration

PHP foreach Loop

The foreach loop works only on arrays, and is used to loop through each key/value pair in an array.

Syntax

foreach ($array as $value) {
  code to be executed;
}

For every loop iteration, the value of the current array element is assigned to $value and the array pointer is moved by one, until it reaches the last array element.

Examples

The following example will output the values of the given array ($colors):

Example

<?php
$colors = array("red", "green", "blue", "yellow");

foreach ($colors as $value) {
echo "$value <br>";
}
?>