PHP - Developer Haseeb

Introduction

Syntax

Variables

DataTypes

Operators

If Else

Loop

Functions

File Handle

Introduction

Syntax

The default file extension for PHP files is “.php“.

A PHP file normally contains HTML tags, and some PHP scripting code.

Below, we have an example of a simple PHP file, with a PHP script that uses a built-in PHP function “echo” to output the text “Hello World!” on a web page:

<!DOCTYPE html>
<html>
<body>

<h1>My first PHP page</h1>

<?php
echo "Hello World!";
?>

</body>
</html>

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)

$txt = "W3Schools.com";
echo "I love " . $txt . "!";

DataTypes

Variables can store data of different types, and different data types can do different things.
PHP supports the following data types:
- String
- Integer
- Float (floating point numbers – also called double)
- Boolean
- Array
- Object
- NULL
- Resource

$x = "Hello world!";
$y = 'Hello world!';

var_dump($x);
echo "<br>";
var_dump($y);

Operators

If Else

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

if (condition) {
  code to be executed if this condition is true;
} elseif (condition) {
  // code to be executed if first condition is false and this condition is true;
} else {
  // code to be executed if all conditions are false;
}

Loop

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

$i = 1;
while ($i < 6) {
  echo $i;
  $i++;
}

Functions

Besides the built-in PHP functions, it is possible to create your own functions.

A function is a block of statements that can be used repeatedly in a program.
A function will not execute automatically when a page loads.
A function will be executed by a call to the function.

function sum($x, $y) {
  $z = $x + $y;
  return $z;
}

echo "5 + 10 = " . sum(5, 10) . "<br>";
echo "7 + 13 = " . sum(7, 13) . "<br>";
echo "2 + 4 = " . sum(2, 4);

File Handle

The readfile() function reads a file and writes it to the output buffer.

Assume we have a text file called “webdictionary.txt”, stored on the server, that looks like this:

AJAX = Asynchronous JavaScript and XML
CSS = Cascading Style Sheets
HTML = Hyper Text Markup Language
PHP = PHP Hypertext Preprocessor
SQL = Structured Query Language
SVG = Scalable Vector Graphics
XML = EXtensible Markup Language

The PHP code to read the file and write it to the output buffer is as follows (the readfile() function returns the number of bytes read on success):

<!DOCTYPE html>
<html>
<body>

<?php
echo readfile(“webdictionary.txt”);
?>

</body>
</html>

+	Addition	$x + $y	Sum of $x and $y	Try it »
–	Subtraction	$x – $y	Difference of $x and $y	Try it »
*	Multiplication	$x * $y	Product of $x and $y	Try it »
/	Division	$x / $y	Quotient of $x and $y	Try it »
%	Modulus	$x % $y	Remainder of $x divided by $y	Try it »
**	Exponentiation	$x ** $y	Result of raising $x to the $y’th power

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