Php Constants And Operators Complete Guide

PHP Constants

In PHP, constants are used to store values that should not change throughout the script. To define a constant, you use the define() function or the const keyword.

Example 1: Using the define() function

<?php
// Define a constant using the define() function
define("GREETING", "Hello, World!");

// Output the value of the constant
echo GREETING;
?>

Explanation:

• We use the define() function to create a constant named GREETING with the value "Hello, World!".
• The echo statement is then used to display the value of this constant.

Example 2: Using the const Keyword

<?php
// Define a constant using the const keyword
const WELCOME = "Welcome to PHP!";

// Output the value of the constant
echo WELCOME;
?>

Explanation:

• We use the const keyword to create a constant named WELCOME with the value "Welcome to PHP!".
• We use echo to display this value.

Example 3: Defining Multiple Constants

<?php
// Define multiple constants
define("PI", 3.14);
define("EULER_NUMBER", 2.718);

// Output the values of the constants
echo "The value of PI is: " . PI . "\n";
echo "The value of Euler's Number is: " . EULER_NUMBER;
?>

Explanation:

• We define two constants: PI with the value 3.14 and EULER_NUMBER with the value 2.718.
• We use string concatenation to display the values of these constants.

PHP Operators

Operators perform operations on variables and other data. Here we will cover basic arithmetic, assignment, comparison, and logical operators.

Example 4: Arithmetic Operators

<?php
$a = 5;
$b = 3;

// Addition
echo $a + $b; // Outputs: 8

// Subtraction
echo "\n" . ($a - $b); // Outputs: 2

// Multiplication
echo "\n" . ($a * $b); // Outputs: 15

// Division
echo "\n" . ($a / $b); // Outputs: 1.6666666666667

// Modulus (remainder)
echo "\n" . ($a % $b); // Outputs: 2
?>

Explanation:

• We define two variables $a and $b.
• We use the + operator to add these numbers and display the result.
• Similarly, we subtract, multiply, divide, and find the modulus using the respective operators.

Example 5: Assignment Operators

<?php
$x = 10;

// Simple assignment
$y = $x;
echo $y; // Outputs: 10

// Addition assignment
$x += 5;
echo "\n" . $x; // Outputs: 15

// Subtraction assignment
$x -= 3;
echo "\n" . $x; // Outputs: 12

// Multiplication assignment
$x *= 2;
echo "\n" . $x; // Outputs: 24

// Division assignment
$x /= 4;
echo "\n" . $x; // Outputs: 6

// Modulus assignment
$x %= 3;
echo "\n" . $x; // Outputs: 0
?>

Explanation:

• We initialize a variable $x with the value 10.
• We use the simple assignment operator = to copy the value from $x to $y.
• We then use addition assignment +=, subtraction assignment -=, multiplication assignment *=, division assignment /=, and modulus assignment %= to update the value of $x accordingly.

Example 6: Comparison Operators

<?php
$a = 5;
$b = 10;

// Equal to
var_dump($a == $b); // Outputs: bool(false)

// Not equal to
var_dump($a != $b); // Outputs: bool(true)

// Identical to
var_dump($a === $b); // Outputs: bool(false)

// Not identical to
var_dump($a !== $b); // Outputs: bool(true)

// Greater than
var_dump($a > $b); // Outputs: bool(false)

// Less than
var_dump($a < $b); // Outputs: bool(true)

// Greater than or equal to
var_dump($a >= $b); // Outputs: bool(false)

// Less than or equal to
var_dump($a <= $b); // Outputs: bool(true)
?>

Explanation:

• We initialize two variables $a and $b.
• We use various comparison operators like ==, !=, ===, !==, >, <, >=, and <= to compare the values and display the results using var_dump.

Example 7: Logical Operators

<?php
$a = true;
$b = false;

// AND operator
var_dump($a && $b); // Outputs: bool(false)

// OR operator
var_dump($a || $b); // Outputs: bool(true)

// XOR operator
var_dump($a xor $b); // Outputs: bool(true)

// NOT operator
var_dump(!$a); // Outputs: bool(false)
?>

Explanation:

• We initialize two boolean variables $a and $b.
• We use logical operators like &&, ||, xor, and ! to manipulate and display the truth value of expressions.