Discuss how to use PHP to complete add, delete, check and modify operations

PHP is a popular server-side programming language that can be used to build rich web applications. Among them, adding, deleting, checking and modifying is one of the most basic and commonly used operations in web application development. Therefore, in this article, we will take a deep dive into how to use PHP to complete CRUD operations so that you can easily start developing web applications.

Step 1: Establish a database

Before adding, deleting, checking, and modifying, you need to create a database first. In this article we will use MySQL as an example. In MySQL, we can use the following SQL statement to create a simple user table:

CREATE TABLE users (

id INT NOT NULL AUTO_INCREMENT,
name VARCHAR(50) NOT NULL,
email VARCHAR(50) NOT NULL,
password VARCHAR(50) NOT NULL,
PRIMARY KEY (id)

);

This statement will create a table named The "users" table contains four columns: id, name, email, and password. Where "id" is an auto-incrementing field, so each new record will have a unique id.

Step 2: Connect to the database

To use PHP to perform add, delete, check and modify operations, we need to connect to the MySQL database first. You can use the following code to connect to the MySQL database:

$servername = "localhost";
$username = "root";
$password = "password";
$dbname = "myDB";

$conn = mysqli_connect($servername, $username, $password, $dbname);

if (!$conn) {

die("Connection failed: " . mysqli_connect_error());

}
echo "Connected successfully";
?>

In the above code, we specified the server name, user name, password and database name. If the connection fails, a connection error message will be output. If the connection is successful, "Connected successfully" will be output.

Step 3: Insert new records

Now that we have successfully connected to the MySQL database, the following is the code on how to insert new records:

$sql = "INSERT INTO users (name, email, password)
VALUES ('John', 'john@example.com', 'password123')";

if (mysqli_query($conn , $sql)) {

echo "New record created successfully";

} else {

echo "Error: " . $sql . "<br>" . mysqli_error($conn);

}
?>

In the above code, we use the INSERT statement to " Insert a new record into the users table. This record contains three fields: name, email, and password. If the insertion is successful, the message "New record created successfully" will be output. If an error occurs, an error message will be output.

Step 4: Query data

We can use the SELECT statement to query the data in the "users" table. The following is the code for how to query data:

$sql = "SELECT id, name, email FROM users";
$result = mysqli_query($conn, $sql);

if (mysqli_num_rows($result) > 0) {

while($row = mysqli_fetch_assoc($result)) {
    echo "id: " . $row["id"]. " - Name: " . $row["name"]. " - Email: " . $row["email"]. "<br>";
}

} else {

echo "0 results";

}
?>

above In the code, we use the SELECT statement to query the id, name, and email columns in the "users" table. If there is data in the result set, use a while loop to output the query results line by line. If the result set is empty, "0 results" is output.

Step 5: Update records

We can use the UPDATE statement to update the records in the "users" table. Here is the code on how to update the record:

$sql = "UPDATE users SET email='john.doe@example.com' WHERE id=1";

if (mysqli_query($conn, $sql)) {

echo "Record updated successfully";

} else {

echo "Error updating record: " . mysqli_error($conn);

}
?>

In the above code, we Update the "email" field of the record with "id" 1 to "john.doe@example.com". If the update is successful, the "Record updated successfully" message is output. Otherwise, an error message is output.

Step 6: Delete records

We can use the DELETE statement to delete records in the "users" table. The following is the code for how to delete records:

$sql = "DELETE FROM users WHERE id=1";

if (mysqli_query($conn, $sql) ) {

echo "Record deleted successfully";

} else {

echo "Error deleting record: " . mysqli_error($conn);

}
?>

In the above code, we use the DELETE statement to delete the "id" of 1 Record. If the deletion is successful, the message "Record deleted successfully" is output. Otherwise, an error message is output.

Summary

The above are the basic operations of PHP to complete additions, deletions, checks and modifications. They are one of the most basic and commonly used operations in Web application development. By studying this article, you should have learned how to use PHP to connect to the database, insert new records, query data, update records, and delete records. Hope this article helps you and achieve more success in web application development.

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