PHP form processing: form data query and filtering

PHP form processing: form data query and filtering

1. Introduction
   In Web development, forms are an important way of interaction. Users can submit data to the server through the form and proceed further. processing. This article will introduce how to use PHP to process the query and filter functions of form data.
2. Form design and submission
   First, we need to design a form that includes query and filtering functions. Common form elements include input boxes, drop-down lists, radio buttons, check boxes, etc., which can be designed according to specific needs. When the user submits the form, the data will be sent to the server in POST or GET mode.

The following is an example of a simple query and filter form:

<form action="process.php" method="POST">
  <label for="name">姓名：</label>
  <input type="text" id="name" name="name">
  
  <label for="gender">性别：</label>
  <select id="gender" name="gender">
    <option value="Male">男</option>
    <option value="Female">女</option>
  </select>
  
  <label for="age">年龄：</label>
  <input type="number" id="age" name="age">
  
  <input type="submit" value="查询">
</form>

3. Server-side processing
   When the user submits the form, the server will receive the form data , we can use PHP to process this data. First, get the form data in the process.php file:

$name = $_POST['name'];
$gender = $_POST['gender'];
$age = $_POST['age'];

Next, we can use this data to query related information in the database. Suppose we have a student table that contains fields such as name, gender, age, etc. The following is a simple database query example:

// 连接数据库
$conn = mysqli_connect('localhost', 'username', 'password', 'database');

// 查询语句
$sql = "SELECT * FROM students WHERE 1=1";

// 添加查询条件
if (!empty($name)) {
  $sql .= " AND name LIKE '%$name%'";
}

if (!empty($gender)) {
  $sql .= " AND gender='$gender'";
}

if (!empty($age)) {
  $sql .= " AND age=$age";
}

// 执行查询
$result = mysqli_query($conn, $sql);

// 处理查询结果
if (mysqli_num_rows($result) > 0) {
  while ($row = mysqli_fetch_assoc($result)) {
    // 处理每一行数据
  }
} else {
  echo "没有找到相关记录";
}

// 关闭数据库连接
mysqli_close($conn);

In the above example, we implement dynamic query by splicing SQL statements. First, we define an initial SELECT statement, and then dynamically add a WHERE clause based on the query conditions submitted by the form.

Finally, we use the mysqli_query function to execute the query, and use the mysqli_num_rows function to get the number of rows in the query result. If there are query results, you can use the mysqli_fetch_assoc function to process the data row by row.

4. Display query results
   The last step is to display the query results to the user. Data can be displayed through HTML tables:

if (mysqli_num_rows($result) > 0) {
  echo "<table>";
  echo "<tr><th>姓名</th><th>性别</th><th>年龄</th></tr>";
  
  while ($row = mysqli_fetch_assoc($result)) {
    echo "<tr>";
    echo "<td>".$row['name']."</td>";
    echo "<td>".$row['gender']."</td>";
    echo "<td>".$row['age']."</td>";
    echo "</tr>";
  }
  
  echo "</table>";
} else {
  echo "没有找到相关记录";
}

In the above code, we loop through each record of the query results and output it in the form of a table.

5. Summary
   This article introduces how to use PHP to process the query and filtering functions of form data. By obtaining form data, dynamically constructing SQL query statements, and displaying query results to users through HTML tables, a complete query and filtering function is realized.

In fact, form processing and data query are common functions in web development, and this article only provides a simple example. In actual development, more code and technology may be required depending on the complexity of specific requirements. However, by mastering the basic processing procedures and related technologies, a good foundation can be provided for subsequent development.

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