Unit 1: Introduction to PHP programming

PHP code sits inside <?php ... ?> tags and statements end with semicolons.

php<?php
$name = "Ana";             // string
$age = 19;                 // integer
$cgpa = 8.6;               // float
$isEnrolled = true;        // boolean
define("COLLEGE", "SBS");  // constant
echo "Hello $name from " . COLLEGE;   // . joins strings
?>

• Variables start with $, are case-sensitive, and need no type declaration (PHP is loosely typed).
• Data types: string, integer, float, boolean, array, object, NULL and resource.
• Operators: arithmetic (+ − × / % **), assignment (=, +=), comparison (==, ===, !=, <, >), logical (&&, ||, !) and string concatenation (.).

php<?php
$marks = 72;
if ($marks >= 75) echo "Distinction";
elseif ($marks >= 60) echo "First division";
else echo "Pass";

for ($i = 1; $i <= 5; $i++) echo $i;
foreach (["BCA", "BBA"] as $course) echo $course;

function area($l, $b = 1) {   // default parameter
    return $l * $b;
}
echo area(5, 4);              // 20
?>

PHP also has while, do…while and switch.

html<form action="welcome.php" method="post">
  Name: <input type="text" name="uname">
  <input type="submit">
</form>

php<?php
$name = htmlspecialchars($_POST["uname"]);   // prevents script injection
echo "Welcome, $name";
?>

• $_GET reads data sent in the URL; $_POST reads data sent in the request body; $_REQUEST reads both.