How to use UPDATE statement in php to modify data in database

In PHP, we can use SQL statements to modify data in the database. More specifically, we can use the UPDATE statement to modify data in one or more tables.

The following is a basic example:

$sql = "UPDATE users SET name='John' WHERE id=1";
mysqli_query($conn, $sql);

In this example, we are modifying a row in the table named "users" that has an ID of 1. We set the row's Name field to John.

It should be noted that we use the WHERE clause to specify which rows are to be changed. If we don't use WHERE clause then all the rows in the table will be changed.

We can also update multiple fields:

$sql = "UPDATE users SET name='John', email='john@example.com' WHERE id=1";
mysqli_query($conn, $sql);

Now, we update both the name and email fields to the new values. If we want to update all rows, we can omit the WHERE clause as shown below:

$sql = "UPDATE users SET name='John'";
mysqli_query($conn, $sql);

This will change the name field of all rows in the "users" table.

It is worth mentioning that we can also use PHP variables to set values ​​in queries:

$name = 'John';
$email = 'john@example.com';

$sql = "UPDATE users SET name='$name', email='$email' WHERE id=1";
mysqli_query($conn, $sql);

We need to pay attention to SQL injection attacks. To prevent this, we should use prepared statements and bind parameters. Here is an example:

$name = 'John';
$email = 'john@example.com';
$id = 1;

$stmt = $conn->prepare("UPDATE users SET name=?, email=? WHERE id=?");
$stmt->bind_param("ssi", $name, $email, $id);
$stmt->execute();

In this example, we use prepared statements and bind parameters. This means we pass the variables into the query instead of placing them directly in the string. Doing so can significantly reduce the risk of SQL injection.

In short, in PHP, we can use SQL statements and prepared statements to modify data in the database. Ensure best practices are always followed to protect our applications from cyberattacks.

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