PHP
updated on: 19-Dec-2022
PHP Basics
Tools
What is PHP
PHP (recursive acronym for PHP: Hypertext Preprocessor) is a widely-used open source general-purpose scripting language that is especially suited for web development and can be embedded into HTML.
Further reading: - Intro. to PHP
What is a PHP File?
- PHP files can contain text, HTML, CSS, JavaScript, and PHP code.
- PHP code are executed on the server, and the result is returned to the browser as plain HTML.
- PHP files have extension “.php”.
What Can PHP Do?
- PHP can generate dynamic page content
- PHP can create, open, read, write, delete, and close files on the server
- PHP can collect form data
- PHP can send and receive cookies
- PHP can add, delete, modify data in your database
- PHP can be used to control user-access
- PHP can encrypt data
With PHP you are not limited to output HTML. You can output images, PDF files, and even Flash movies. You can also output any text, such as XHTML and XML.
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. Download it from the official PHP resource: www.php.net
- PHP is easy to learn and runs efficiently on the server side
Install XAMPP Server
XAMPP is the most popular PHP development environment. XAMPP is a completely free, easy to install Apache distribution containing MariaDB, PHP, and Perl. The XAMPP open source package has been set up to be incredibly easy to install and to use.
- Download XAMPP server https://www.apachefriends.org/download.html
- Install XAMPP server
- Open XAMPP Control Panel
- Click on the “Start” button next to “Apache” to start your Apache Web server. When Apache is running, the word “Running” will appear next to it, highlighted in green
- Also start “MySQL” if your PHP scripts depend on a MySQL database to run.
- Place your PHP files in the “htdocs” folder located under the “XAMMP” folder on your C: drive. The file path is “C:\xampp\htdocs” for your Web server.
- Open your Web browser and enter “localhost” into the address box. type name of your PHP file.
- Create any folders you need to test PHP files in under the “htdocs” folder. If you create a folder named “scripts,” then use the address “localhost/scripts” to open them in your browser.
Example #1 an introductory example
<!DOCTYPE html>
<html>
<head>
<title>Example</title>
</head>
<body>
<?php
echo "Hi, I'm a PHP script!";
?>
</body>
</html>
phpinfo — Outputs information about PHP’s configuration
Example #2 phpinfo example
<?php
// Show all information, defaults to INFO_ALL
phpinfo();
// Show just the module information.
// phpinfo(8) yields identical results.
phpinfo(INFO_MODULES);
?>
In PHP, all keywords (e.g. if, else, while, echo, etc.), classes, functions, and user-defined functions are NOT case-sensitive.
Example #3 echo example
<?php
ECHO "Hello World!<br>";
echo "Hello World!<br>";
EcHo "Hello World!<br>";
?>
Variables
- Variables are used to store data, like string of text, numbers, etc.
- Variable values can change over the course of a script.
- In PHP, a variable does not need to be declared before adding a value to it.
- PHP automatically converts the variable to the correct data type, depending on its value
- After declaring a variable it can be reused throughout the code.
- The assignment operator (=) used to assign value to a variable.
- all variable names are case-sensitive.
In PHP variable can be declared as: $var_name = value;
Further reading: https://www.tutorialrepublic.com/php-tutorial/php-variables.php
Example #1 variable names
<?php
$color = "red";
$COLOR="GREEN";
echo "My car is " . $color . "<br>";
echo "My house is " . $COLOR . "<br>";
echo "My boat is " . $coLOR . "<br>";
?>
Example #2 disply of variable using echo statement
<?php
$txt = "W3Schools.com";
echo "I love $txt!";
// produce the same output
echo "<br>";
echo "I love " . $txt . "!";
?>
Example #3 variable example
<?php
$x = 5;
$y = 4;
echo $x + $y;
?>
Variable scope
- The scope of a variable is the context within which it is defined.
- For the most part all PHP variables only have a single scope.
- This single scope spans included and required files as well.
Further reading: https://www.php.net/manual/en/language.variables.scope.php
Local scope variable
Example #1 local scope variable example
<?php
function myTest() {
$x = 5; // local scope
echo "<p>Variable x inside function is: $x</p>";
}
myTest();
// using x outside the function will generate an error
echo "<p>Variable x outside function is: $x</p>";
?>
Global scope variable
Example #2 global scope variable example
<?php
$x = 5; // global scope
function myTest() {
// using x inside this function will generate an error
echo "<p>Variable x inside function is: $x</p>";
}
myTest();
echo "<p>Variable x outside function is: $x</p>";
?>
The global keyword
Example #3 using global
<?php
$x = 5; // global scope
$y = 10;
function myTest() {
global $x, $y; // use global scope variable in function
$y = $x + $y;
}
myTest();
echo $y; // outputs 15
?>
$GLOBALS - The $GLOBALS array is an associative array with the name of the global variable being the key and the contents of that variable being the value of the array element.
- $GLOBALS exists in any scope, this is because $GLOBALS is a superglobal.
Example #4 using $GLOBALS instead of global example
<?php
$x = 5;
$y = 10;
function myTest() {
$GLOBALS['y'] = $GLOBALS['x'] + $GLOBALS['y'];
}
myTest();
echo $y; // outputs 15
?>
Using static variables
- A static variable exists only in a local function scope, but it does not lose its value when program execution leaves this scope.
Example #5 Example demonstrating need for static variables
<?php
function test()
{
$a = 0;
echo $a;
$a++;
}
?>
Example #6 use of static variables
<?php
function myTest() {
static $x = 0;
echo $x . "<br \>";
$x++;
}
myTest();
myTest();
myTest();
myTest();
?>
String functions
strlen
Example #1 Get The Lenght of a String
<?php
echo "Length of a String: ";
echo strlen("Hello world!"); // outputs 12
?>
str_word_count
Example #2 Count The Number of Words in a String
<?php
echo "<br /> Count Words: ";
echo str_word_count("Hello world!"); // outputs 2
?>
strrev
Example #3 Reverse a String
<?php
echo "<br />Reverse a String: ";
echo strrev("Hello world!"); // outputs !dlrow olleH
?>
strpos
Example #4 Search For a Specific Text Within a String
<?php
echo "<br />Position: ";
echo strpos("Hello world!", "world"); // outputs 6
?>
str_replace
Example #5 Replace Text Within a String
<?php
echo "<br />Replace: ";
echo str_replace("world", "PHP", "Hello world!"); // outputs Hello Dolly!
?>
Comments
Example #1 Comments example
<!DOCTYPE html>
<html>
<body>
<?php
// This is a single-line comment
# This is also a single-line comment
/*
This is a multiple-lines comment block
that spans over multiple
lines
*/
// You can also use comments to leave out parts of a code line
$x = 5 /* + 15 */ + 5;
$name = "Muhammad Ahmad Nasir";
echo "<h2>$name</h2>";
echo '<h1>' .$x. '</h1>';
?>
</body>
</html>
define function
define — Defines a named constant
Further reading: - https://www.php.net/manual/en/function.define.php
Example #1 Defines a named constant
<!DOCTYPE html>
<html lang="en">
<head>
<title>PHP - Contants</title>
</head>
<body>
<?php
// define(name, value, case-insensitive)
// case-insensitive: Specifies whether the constant name should be case-insensitive. Default is false
define("GREETING", "Welcome to Department of CS & IT!");
function myTest() {
echo GREETING;
}
myTest();
?>
</body>
</html>
functions
Example #1 Function examples
<!DOCTYPE html>
<html lang="en">
<head>
<title>PHP - Functions</title>
</head>
<body>
<?php
// Syntax
//
/*function functionName() {
code to be executed;
}*/
//
// Example1
//
function writeMsg() {
echo "Hello world!";
}
writeMsg(); // call the function
//
// Example2 - By Argument
//
function familyName($fname) {
echo "$fname Nasir" . "<br>";
}
familyName("Muhammad"); // call
familyName("Ali");
familyName("Zeeshan");
// Example3 - By two arguments
//
//
function familyName($fname, $year) {
echo "$fname. Born in $year <br>";
}
familyName("Muhammad Ali", "1975");
familyName("Muhammad Nasir", "1978");
familyName("Muhammad Hamza", "1983");*/
//
// Example 4 - Default Argument Value
//
function setHeight($minheight = 50) {
echo "The height is : $minheight <br>";
}
setHeight(350);
setHeight(); // will use the default value of 50
setHeight(135);
setHeight(80);
//
// Example 5 - Returning Values
//
function sum($x, $y) {
$z = $x + $y;
return $z;
}
$i = sum(5, 10);
echo "5 + 10 = " . $i . "<br>";
echo "7 + 13 = " . sum(7, 13) . "<br>";
?>
</body>
</html>
References
Muhammad Yasir Bhutta