PHP Syntax and Basic Concepts
PHP Syntax And Code Structure
1. PHP Syntax Overview:
Tags:
- PHP code is enclosed within
<?php ?> - Alternatively,
<? ?>
Example:
echo "Hello, World!";
?>
Comments:
- Comments in PHP can be single-line (
//) or multi-line (/* */). - Comments are not displayed in the output and are used for code documentation and readability.
Example:
/*
This is a
multi-line comment
*/
?>
2. Variables and Data Types:
Variables:
- Variables in PHP start with a dollar sign (
$) followed by the variable name. - Variable names are case-sensitive and must start with a letter or underscore.
Example:
$name = "John";
$age = 25;
?>
Data Types:
- PHP supports various data types including strings, integers, floats, booleans, arrays, and objects.
- Data types are dynamically assigned based on the value assigned to a variable.
Example:
$name = "John"; // String
$age = 25; // Integer
$height = 5.11; // Float
$isStudent = true; // Boolean
?>
3. Control Structures:
If-Else Statements:
- If-else statements are used for conditional execution of code blocks based on certain conditions.
Example:
$grade = 85;
if ($grade >= 60) {
echo "Pass";
} else {
echo "Fail";
}
?>
Loops:
- PHP supports different types of loops including
for,while,do-while, andforeachloops.
Example (for loop):
for ($i = 1; $i <= 5; $i++) {
echo $i;
}
?>
4. Functions:
Declaring Functions:
- Functions are defined using the
functionkeyword followed by the function name and parameters. - Functions can return values using the
returnstatement.
Example:
function greet($name) {
return "Hello, $name!";
}
echo greet("John");
?>
Built-in Functions:
- PHP provides a wide range of built-in functions for common tasks such as string manipulation, array operations, date and time handling, etc.
Example:
$str = "Hello, World!";
echo strtoupper($str); // Outputs: HELLO, WORLD!
?>
5. PHP in HTML:
Embedding PHP in HTML:
- PHP code can be embedded within HTML code using the
<?php ?> - This allows dynamic generation of HTML content based on server-side logic.
Example:
<!DOCTYPE html>
<html>
<head>
<title>PHP Example</title>
</head>
<body>
<h1><?php echo "Hello, World!"; ?></h1>
</body>
</html>Using PHP Variables in HTML:
- PHP variables can be directly used within HTML code by placing them within the PHP tags.
Example:
<!DOCTYPE html>
<html>
<head>
<title>PHP Example</title>
</head>
<body>
<p>Welcome, <?php echo $name; ?>!</p>
</body>
</html>Practice Excercise Practice now
Working With Variables, Data Types, And Operators In PHP
Working with Variables, Data Types, and Operators in PHP
PHP is a versatile scripting language widely used for web development. Understanding how to work with variables, data types, and operators is fundamental to writing PHP scripts effectively. Let's delve into each aspect:
1. Variables in PHP:
Variables in PHP are used to store data values. They are declared using the $ symbol followed by the variable name. PHP variables are case-sensitive and must start with a letter or an underscore.
Example:
$name = "John";
$age = 30;
?>
2. Data Types in PHP:
PHP supports various data types, including:
- String: A sequence of characters enclosed within quotes.
- Integer: A whole number without decimals.
- Float: A number with a decimal point or an exponent.
- Boolean: Represents true or false values.
- Array: A collection of key-value pairs.
- Object: Instances of user-defined classes.
- NULL: Represents a null value.
- Resource: Special variables holding references to external resources.
Example:
$name = "John"; // String
$age = 30; // Integer
$height = 6.1; // Float
$isStudent = true; // Boolean
$grades = array(80, 85, 90); // Array
?>
3. Operators in PHP:
PHP supports various operators for performing operations on variables and values. These include:
- Arithmetic Operators: Addition (+), Subtraction (-), Multiplication (*), Division (/), Modulus (%), Increment (++), Decrement (--).
- Assignment Operators: Assigns a value to a variable (e.g., =, +=, -=, *=, /=).
- Comparison Operators: Compares values (e.g., ==, !=, <, >, <=, >=).
- Logical Operators: Performs logical operations (e.g., &&, ||, !).
- String Operators: Concatenates strings (e.g., .).
- Array Operators: Concatenates arrays (e.g., +).
Example:
$x = 10;
$y = 5;
// Arithmetic operators
$sum = $x + $y; // 15
$difference = $x - $y; // 5
$product = $x * $y; // 50
$quotient = $x / $y; // 2
$remainder = $x % $y; // 0
// Assignment operators
$x += 5; // $x is now 15
$y -= 2; // $y is now 3
// Comparison operators
$is_equal = ($x == $y); // false
$is_greater = ($x > $y); // true
// Logical operators
$is_true = ($x > 0 && $y > 0); // true
$is_false = ($x < 0 || $y < 0); // false
// String operators
$name = "John";
$greeting = "Hello, " . $name; // "Hello, John"
// Array operators
$grades1 = array(80, 85);
$grades2 = array(90, 95);
$combined_grades = $grades1 + $grades2; // [80, 85, 90, 95]
?>
Practice Excercise Practice now
Using Control Structures Such As Conditionals And Loops In PHP Scripts
Using Control Structures in PHP Scripts
Control structures are essential elements in programming languages like PHP, allowing developers to control the flow of execution based on various conditions and to iterate through data efficiently using loops. Let's delve into how these control structures work with examples.
1. Conditional Statements in PHP:
Conditional statements enable PHP scripts to make decisions based on conditions. They allow the execution of specific blocks of code only when certain conditions are met.
a. The if Statement:
The if statement is the most basic conditional statement in PHP. It executes a block of code if a specified condition evaluates to true.
$age = 20;
if ($age >= 18) {
echo "You are eligible to vote.";
}
?>
b. The else Statement:
The else statement works in conjunction with the if statement. It executes a block of code if the if condition evaluates to false.
$age = 15;
if ($age >= 18) {
echo "You are eligible to vote.";
} else {
echo "You are not eligible to vote.";
}
?>
c. The elseif Statement:
The elseif statement allows you to add additional conditions to the if statement. It provides an alternative when the original condition is false.
$age = 25;
if ($age < 18) {
echo "You are a minor.";
} elseif ($age >= 18 && $age < 65) {
echo "You are an adult.";
} else {
echo "You are a senior citizen.";
}
?>
d. The switch Statement:
The switch statement evaluates an expression against multiple possible cases. It provides an alternative to multiple if-elseif-else statements.
$day = "Monday";
switch ($day) {
case "Monday":
echo "Today is Monday.";
break;
case "Tuesday":
echo "Today is Tuesday.";
break;
default:
echo "It's neither Monday nor Tuesday.";
}
?>
2. Loops in PHP:
Loops allow PHP scripts to iterate through data repeatedly. They are used to execute a block of code multiple times until a specified condition is met.
a. The for Loop:
The for loop executes a block of code a specified number of times. It consists of three parts: initialization, condition, and increment/decrement.
for ($i = 1; $i <= 5; $i++) {
echo "The number is: $i <br>";
}
?>
b. The while Loop:
The while loop executes a block of code as long as a specified condition is true. It evaluates the condition before executing the block.
$i = 1;
while ($i <= 5) {
echo "The number is: $i <br>";
$i++;
}
?>
c. The do-while Loop:
The do-while loop is similar to the while loop but guarantees that the block of code is executed at least once before checking the condition.
$i = 1;
do {
echo "The number is: $i <br>";
$i++;
} while ($i <= 5);
?>
d. The foreach Loop:
The foreach loop is used to iterate over the elements of an array. It simplifies the process of looping through arrays.
$colors = array("Red", "Green", "Blue");
foreach ($colors as $color) {
echo "Color: $color <br>";
}
?>
Practical Example:
Let's create a PHP script that generates a multiplication table for a given number using a loop:
$number = 5;
echo "<h2>Multiplication Table for $number</h2>";
echo "<table border='1'>";
for ($i = 1; $i <= 10; $i++) {
echo "<tr><td>$number x $i</td><td>=</td><td>" . ($number * $i) . "</td></tr>";
}
echo "</table>";
?>
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