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PHP & MySql
for ($i = 0; $i < 5; $i++) {
// code to be executed
}
while loop: A while loop is used when you want to repeat a block of code as long as a certain condition is true. The condition is evaluated before each iteration. If the condition is false initially, the code block will not execute. Here’s an example:
$i = 0;
while ($i < 5) {
// code to be executed
$i++;
}
do-while loop: A do-while loop is similar to a while loop, but the condition is evaluated after executing the code block. This guarantees that the code block is executed at least once, even if the condition is initially false. Here’s an example:
$i = 0;
do {
// code to be executed
$i++;
} while ($i < 5);
foreach loop: A foreach loop is specifically used for iterating over arrays or traversing the elements of an object. It automatically assigns the current element to a variable, which you can use within the loop. Here’s an example:
$numbers = [1, 2, 3, 4, 5];
foreach ($numbers as $number) {
// code to be executed
}
In this loop, $number represents the current element of the array $numbers in each iteration.
These loops provide different ways to control the flow of execution and repeat code based on specific conditions, allowing you to handle various looping scenarios in PHP.
function addNumbers($num1, $num2) {
$sum = $num1 + $num2;
return $sum;
}
In the above example, the function addNumbers takes two parameters ($num1 and $num2) and calculates their sum. The return statement is used to send back the result.
To call a function, you simply use its name followed by parentheses, and you can optionally pass arguments inside the parentheses. Here’s an example of calling the addNumbers function:
$result = addNumbers(5, 3);
echo $result; // Output: 8
In this case, the function is called with arguments 5 and 3, and the returned value is stored in the variable $result. Finally, the result is echoed, resulting in 8 being displayed.
Functions in PHP can have optional parameters, default parameter values, and can also return values using the return statement. They provide a way to structure and reuse code, making your PHP programs more efficient and maintainable.
class Car {
public $color;
public $brand;
public function startEngine() {
echo "The car engine is started.";
}
}
In the above example, the Car class has two properties ($color and $brand) and one method (startEngine()). The properties represent the characteristics of a car, while the method represents a behavior.
To create an object from a class, you use the new keyword followed by the class name and parentheses. Here’s an example of creating a Car object:
$myCar = new Car();
Now, you can access the properties and methods of the object using the object’s name followed by the arrow operator (->). Here’s an example:
$myCar->color = "Blue";
$myCar->brand = "Toyota";
echo $myCar->color; // Output: Blue
$myCar->startEngine(); // Output: The car engine is started.
In this example, the properties color and brand of the $myCar object are set to “Blue” and “Toyota”, respectively. The echo statement displays the value of the color property, and the startEngine() method is called, resulting in the corresponding output.
OOP in PHP allows you to create reusable and structured code by defining classes and creating objects from those classes. It provides a powerful way to model complex systems and manage code complexity.
include 'filename.php';
2. require statement: The require statement also includes and evaluates the specified file, but it has a stricter behavior compared to include. If the file is not found or an error occurs during inclusion, a fatal error is triggered, and the script execution is halted. It means that if the required file is missing or contains errors, the script will terminate. The syntax for the require statement is as follows:
require 'filename.php';
To summarize:
Use
includewhen you want to include a file that is not crucial for the script’s functionality, and you want the script to continue execution even if the file is not found or contains errors.Use
requirewhen you want to include a file that is essential for the script’s functionality, and you want the script to terminate if the file is not found or contains errors.
Both include and require statements can include files with PHP code, HTML, or any other text content. It’s important to choose the appropriate statement based on the importance of the file and the desired error handling behavior.
$host = 'localhost';
$username = 'your_username';
$password = 'your_password';
$database = 'your_database';
$connection = mysqli_connect($host, $username, $password, $database);
if (!$connection) {
die('Connection failed: ' . mysqli_connect_error());
}
2. Perform CRUD operations:
Create: To insert data into a database table, you can use SQL INSERT statements. You need to construct the SQL query and execute it using the database connection. Here’s an example of inserting a new record into a
userstable:
$name = 'John Doe';
$email = 'john@example.com';
$sql = "INSERT INTO users (name, email) VALUES ('$name', '$email')";
$result = mysqli_query($connection, $sql);
if ($result) {
echo "Record inserted successfully.";
} else {
echo "Error: " . mysqli_error($connection);
}
Read: To fetch data from a database table, you can use SQL SELECT statements. Again, construct the SQL query and execute it. Here’s an example of retrieving all records from a
userstable:
$sql = "SELECT * FROM users";
$result = mysqli_query($connection, $sql);
if (mysqli_num_rows($result) > 0) {
while ($row = mysqli_fetch_assoc($result)) {
echo "Name: " . $row['name'] . ", Email: " . $row['email'] . "<br>";
}
} else {
echo "No records found.";
}
Update: To update existing data in a database table, you can use SQL UPDATE statements. Construct the SQL query with the desired changes and execute it. Here’s an example of updating a record in the
userstable:
$id = 1;
$newName = 'Jane Smith';
$sql = "UPDATE users SET name = '$newName' WHERE id = $id";
$result = mysqli_query($connection, $sql);
if ($result) {
echo "Record updated successfully.";
} else {
echo "Error: " . mysqli_error($connection);
}
Delete: To remove data from a database table, you can use SQL DELETE statements. Construct the SQL query with the appropriate condition and execute it. Here’s an example of deleting a record from the
userstable:
$id = 1;
$sql = "DELETE FROM users WHERE id = $id";
$result = mysqli_query($connection, $sql);
if ($result) {
echo "Record deleted successfully.";
} else {
echo "Error: " . mysqli_error($connection);
}
3. Close the database connection: After you have finished performing database operations, it’s good practice to close the database connection. This frees up resources and ensures proper cleanup. Use the mysqli_close() function to close the connection:
mysqli_close($connection);
Remember to handle errors
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