Introduction to PHP:
PHP was originally created by Danish-Canadian programmer Rasmus Lerdorf in 1994. The PHP reference implementation is now produced by The PHP Group. PHP originally stood for Personal Home Page but now it stands for the recursive acronym, PHP: Hypertext Preprocessor. Popular websites like Facebook, Yahoo, Wikipedia etc. are developed using PHP.PHP
is
a widely-used open source
general-purpose scripting language for web development. It allows web
developers to create dynamic content that interacts with databases. PHP is
basically used for developing web based software applications.
PHP
is a server side scripting language
that is embedded in HTML. It is used to manage dynamic content, databases,
session tracking, even build entire e-commerce sites. PHP is mainly focused on
server-side scripting so you can collect form data, generate dynamic page
content, or send and receive cookies. Code is executed in a server that is why
you’ll have to install a sever-like environment enabled by programs like XAMPP
which is an Apache distribution.
XAMPP Setup:
XAMPP is a free and open source cross-platform web server solution developed by Apache Friends, consisting mainly of the Apache HTTP Server, MariaDB database, and interpreters for scripts written in the PHP and Perl programming languages. In order to make your PHP code execute locally, first install XAMPP.
- Download XAMPP
- Install the program (check the technologies you want during installation)
- Open XAMPP and click on "Start" on Apache and MySQL (when working with databases)
Characteristics
of PHP:
- Simplicity
- Efficiency
- Security
- Flexibility
- Familiarity
Advantages of PHP:
Since PHP is designed for the web in the first place, it brings many advantages to web development:
- Simple: PHP is quite easy to learn and get started.
- Fast: PHP websites typically run very fast.
- Stable: PHP is stable since it has been in existence for a long time.
- Open-source and free: PHP is open source and free. It means that you don’t have to pay a license fee to use PHP to develop software products.
- Community support: PHP has an active online community that helps you whenever you face an issue.
Uses of PHP:
Here are a few
applications of PHP:
Server-side
scripting: This is the most used and main target for PHP. You
need three things to make this work the way you need it. The PHP parser (CGI or
server module), a web server and a web browser. You need to run the web server
where. You can access the PHP program output with a web browser, viewing the
PHP page through the server.
Command
line scripting: You can make a PHP script to run it
without any server or browser. You only need the PHP parser to use it this way.
This type of usage is ideal for scripts regularly executed using cron (on
Linux) or Task Scheduler (on Windows). These scripts can also be used for
simple text processing tasks.
Writing
desktop applications : PHP may not the very best language to
create a desktop application with a graphical user interface, but if you know
PHP very well, and would like to use some advanced PHP features in your
client-side applications you can also use PHP-GTK to write such programs. You
also have the ability to write cross-platform applications this way.
How PHP Works:
First, the web browser sends an HTTP request to the web server, e.g., index.php.
Second, the PHP preprocessor that locates on the web server processes PHP code to generate the HTML document.
Third, the web server sends the HTML document back to the web browser.
Variables in PHP:
- Any type of variable in PHP starts with a leading dollar sign ($).
- Variables are assigned with the = operator, with the variable on the left-hand side and the expression to be evaluated on the right.
- Variables can, but do not need, to be declared before assignment.
- Variables in PHP do not have intrinsic types - a variable does not know in advance whether it will be used to store a number or a string of characters.
- Variables used before they are assigned have default values.
The main data types used to construct variables are:
- Integers: whole numbers like 23, 1254, 964 etc
- Doubles: floating-point numbers like 46.2, 733.21 etc
- Booleans: only two possible values, true or false
- Strings: set of characters, like ‘PHP supports string’
- Arrays: named and indexed collections of other values
- Objects: instances of predefined classes
Operators and Expressions:
PHP language supports following type of operators.
- Arithmetic Operators
- Comparison Operators
- Logical Operators
- Assignment Operators
- Conditional (or ternary) Operators
Conditional Statement:
Conditional statements are used to execute different
code based on different conditions.
If
Statement:
The if
statement executes a piece of code if a condition is true.
Syntax:
if (condition)
{
// code to be executed in case the condition is true
}
Example:
<?php
$year=2020;
if($year %4==0)
{
echo
"$year is a leap year";
}
?>
Output:
2020
is a leap year
If. . . Else statement :
The If. . . Else statement executed a piece of code
if a condition is true and another piece of code if the condition is false.
Syntax:
if
(condition)
{
// code to be
executed in case the condition is true
}
else
{
// code to be executed in case the condition is
false
}
Example:
<?php
$num=12;
if($num%2==0)
{
echo
"$num is even number";
}
else
{
echo
"$num is odd number";
}
?>
Output:
12
is even number
If.
. . elseif. . . else statement:
This kind of
statement is used to define what should be executed in the case when two or
more conditions are present.
Syntax:
if
(condition1)
{
// code to be
executed in case condition1 is true
}
elseif (condition2)
{
// code to be executed in case condition2 is true
}
else
{
// code to be executed in case all conditions are
false
}
Example:
<?php
$marks=80;
if ($marks<40)
{
echo
"fail";
}
else if ($marks>=40 && $marks<50)
{
echo
"D grade";
}
else if ($marks>=50 && $marks<60)
{
echo
"C grade";
}
else if ($marks>=60 && $marks<70)
{
echo
"B grade";
}
else if ($marks>=70 && $marks<80)
{
echo
"A grade";
}
else if ($marks>=80 && $marks<100)
{
echo
"A+ grade";
}
else
{
echo "Invalid
input";
}
?>
Output:
A+
grade
Iteration
in PHP (Loops in PHP):
In PHP, just like any other programming language,
loops are used to execute the same code block for a specified number of times.
Except for the common loop types (for, while, do. . . while), PHP also support
foreach loops.
For
Loop:
The for loop
is used when the programmer knows in advance how many times the block of code
should be executed. This is the most common type of loop encountered in almost
every programming language.
Syntax:
{
//code to be executed
}
Example:
<?php
for($x=1;$x<=10;$x++)
{
echo
"The number is: $x <br>";
}
?>
Output:
The
number is: 1
The number is: 2
The number is: 3
The number is: 4
The number is: 5
The number is: 6
The number is: 7
The number is: 8
The number is: 9
The number is: 10
Example:
<?php
for($x=10;$x<=100;$x=$x+10)
{
echo "The number is: $x
<br>";
}
?>
Output:
The
number is: 10
The number is: 20
The number is: 30
The number is: 40
The number is: 50
The number is: 60
The number is: 70
The number is: 80
The number is: 90
The number is: 100
While
Loop:
The while loop is used when we want to execute a
block of code as long as a test expression continues to be true.
Syntax:
while(condition)
{
//code to be executed
}
Example:
<?php
$x=1;
while($x <=10)
{
echo
" The number is : $x <br>";
$x++;
}
?>
Output:
The
number is : 1
The number is : 2
The number is : 3
The number is : 4
The number is : 5
The number is : 6
The number is : 7
The number is : 8
The number is : 9
The number is : 10
Do.
. . While loop:
The do...while loop is used when we want to execute
a block of code at least once and then as long as a test expression is true.
Syntax:
do
{
//code to be executed
}
while(condition);
Example:
<?php
$x=1;
do
{
echo
"The number is: $x <br>";
$x++;
}
while($x<=10);
?>
Output:
The
number is: 1
The number is: 2
The number is: 3
The number is: 4
The number is: 5
The number is: 6
The number is: 7
The number is: 8
The number is: 9
The number is: 10
Foreach Loop:
It works only on
array and object. It will issue an error if you try to use it with the
variables of different datatype. It provides an easiest way to iterate
the elements of an array.
Syntax:
foreach ($array as $value)
{
code to be executed;
}
Example:
<?php
//declare array
$days=
array("Sunday","Monday","Tuesday","Wednesday",
"Thursday","Friday","Saturday");
//access array elements using foreach loop
foreach($days as $value)
{
echo
"$value <br>";
}
?>
Output:
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
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