Batch delete in php

In PHP applications, operating databases is a common task. There are many situations where we need to delete multiple data rows in the database. This is batch deletion. In this article, I will show you how to implement bulk delete operations in PHP.

1. Connect to the database

First, we need to connect to the database. Use the following function:

$conn = mysqli_connect("localhost", "my_user", "my_password", "my_db");

This will connect to the database named "my_db". You need to change it to your own database name and provide the correct username and password.

2. Get the selected data rows

Before batch deletion, we need to get the user-selected data rows. For this process we need to use an HTML form and some JavaScript code.

The following is a sample HTML form:

<form method="post" id="deleteForm">
  <table>
    <thead>
      <tr>
        <th>ID</th>
        <th>Name</th>
        <th>Delete</th>
      </tr>
    </thead>
    <tbody>
      <tr>
        <td>1</td>
        <td>John</td>
        <td><input type="checkbox" name="ids[]" value="1"></td>
      </tr>
      <tr>
        <td>2</td>
        <td>Jane</td>
        <td><input type="checkbox" name="ids[]" value="2"></td>
      </tr>
      <tr>
        <td>3</td>
        <td>Bob</td>
        <td><input type="checkbox" name="ids[]" value="3"></td>
      </tr>
    </tbody>
  </table>
  <button type="submit">Delete</button>
</form>

This form has a column of checkboxes, each with a unique value (row ID). When the user selects rows of data to be deleted, the IDs of those rows are added to a form element named "ids[]". The name is an array because we will be selecting multiple values.

Now, we need to write some JavaScript code to get the value selected by the user and pass it to the PHP script behind the scenes.

document.getElementById('deleteForm').addEventListener('submit', function(event) {
  event.preventDefault();
  var selected = document.getElementsByName('ids[]');
  var ids = [];
  for (var i = 0; i < selected.length; i++) {
    if (selected[i].checked) {
      ids.push(selected[i].value);
    }
  }
  // Send selected ids to PHP script for processing
  var request = new XMLHttpRequest();
  request.open('POST', 'delete.php', true);
  request.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded; charset=UTF-8');
  request.onload = function() {
    if (request.status >= 200 && request.status < 400) {
      // Success
      console.log(request.responseText);
    } else {
      // Error
      console.log('Error');
    }
  };
  request.onerror = function() {
    // Connection error
    console.log('Connection Error');
  };
  request.send('ids=' + JSON.stringify(ids));
});

This code sets up a "submit" event listener that will run when the user clicks the "Delete" button. First, it gets all checkboxes named "ids[]". Next, it creates an array containing the row IDs selected by the user. It then uses AJAX to send the array of identifiers to a PHP script named "delete.php". Finally, when the script returns a response, it prints the response content on the console.

3. Handling delete requests

Now, we need to write PHP code to handle the request. In our JavaScript code above, we send the array of identifiers to the script as a JSON string. In PHP, we can use the following code to decode a JSON string into a PHP array:

$ids = json_decode($_POST['ids']);

Next, we need to use a loop to delete each data row:

foreach ($ids as $id) {
  $sql = "DELETE FROM users WHERE id=$id";
  mysqli_query($conn, $sql);
}

This loop iterates through for each ID, and use a SQL query to delete the corresponding rows from the "users" table.

4. Full code example

The following is the complete PHP script:

In this script, we first connect to the database and then we will Character array is decoded into a PHP array. Next, we use a loop to delete each data row. Finally, we output a success message.

5. Summary

In this article, we learned how to implement batch deletion operations in PHP. We use an HTML form and JavaScript code to get the row of data selected by the user, and then use PHP code to handle the request. Bulk deletion is often a necessary feature, and in PHP applications you can easily implement it using the techniques we've covered.

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