PHP MySQL Ajax 搜索

In this tutorial you'll learn how to create a live MySQL database search feature using PHP and Ajax.

## Ajax Live Database Search
You can create a simple live database search functionality utilizing the Ajax and PHP, where the search results will be displayed as you start typing some character in search input box.

In this tutorial we're going to create a live search box that will search the countries table and show the results asynchronously. But, first of all we need to create this table.

### Step 1: Creating the Database Table
Execute the following SQL query to create the countries table in your MySQL database.

```sql
CREATE TABLE countries (
    id INT NOT NULL PRIMARY KEY AUTO_INCREMENT,
    name VARCHAR(50) NOT NULL
);
```
After creating the table, you need to populate it with some data using the [SQL INSERT statement](http://www.bixiaguangnian.com/manual/sql/3392.html "SQL INSERT statement"). Alternatively, you can download the prepopulated countries table by clicking the download button and import it in your MySQL database.

Please check out the tutorial on [SQL CREATE TABLE statement](http://www.bixiaguangnian.com/manual/sql/3390.html "SQL CREATE TABLE statement") for the detailed information about syntax for creating tables in MySQL database system.

### Step 2: Creating the Search Form
Now, let's create a simple web interface that allows user to live search the names of countries available in our countries table, just like an autocomplete or typeahead.

Create a PHP file named "search-form.php" and put the following code inside of it.

```php
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>PHP Live MySQL Database Search</title>
<style>
    body{
        font-family: Arail, sans-serif;
    }
    /* Formatting search box */
    .search-box{
        width: 300px;
        position: relative;
        display: inline-block;
        font-size: 14px;
    }
    .search-box input[type="text"]{
        height: 32px;
        padding: 5px 10px;
        border: 1px solid #CCCCCC;
        font-size: 14px;
    }
    .result{
        position: absolute;        
        z-index: 999;
        top: 100%;
        left: 0;
    }
    .search-box input[type="text"], .result{
        width: 100%;
        box-sizing: border-box;
    }
    /* Formatting result items */
    .result p{
        margin: 0;
        padding: 7px 10px;
        border: 1px solid #CCCCCC;
        border-top: none;
        cursor: pointer;
    }
    .result p:hover{
        background: #f2f2f2;
    }
</style>
<script src="https://code.jquery.com/jquery-3.5.1.min.js"></script>
<script>
$(document).ready(function(){
    $('.search-box input[type="text"]').on("keyup input", function(){
        /* Get input value on change */
        var inputVal = $(this).val();
        var resultDropdown = $(this).siblings(".result");
        if(inputVal.length){
            $.get("backend-search.php", {term: inputVal}).done(function(data){
                // Display the returned data in browser
                resultDropdown.html(data);
            });
        } else{
            resultDropdown.empty();
        }
    });
    
    // Set search input value on click of result item
    $(document).on("click", ".result p", function(){
        $(this).parents(".search-box").find('input[type="text"]').val($(this).text());
        $(this).parent(".result").empty();
    });
});
</script>
</head>
<body>
    <div class="search-box">
        <input type="text" autocomplete="off" placeholder="Search country..." />
        <div class="result"></div>
    </div>
</body>
</html>
```

Every time the content of search input is changed or keyup event occur on search input the jQuery code (line no-47 to 67) sent an Ajax request to the "backend-search.php" file which retrieves the records from countries table related to the searched term. Those records later will be inserted inside a `<div>` by the jQuery and displayed on the browser.

### Step 3: Processing Search Query in Backend
And here's the source code of our "backend-search.php" file which searches the database based on query string sent by the Ajax request and send the results back to browser.

```sql
<?php
/* Attempt MySQL server connection. Assuming you are running MySQL
server with default setting (user 'root' with no password) */
$link = mysqli_connect("localhost", "root", "", "demo");
 
// Check connection
if($link === false){
    die("ERROR: Could not connect. " . mysqli_connect_error());
}
 
if(isset($_REQUEST["term"])){
    // Prepare a select statement
    $sql = "SELECT * FROM countries WHERE name LIKE ?";
    
    if($stmt = mysqli_prepare($link, $sql)){
        // Bind variables to the prepared statement as parameters
        mysqli_stmt_bind_param($stmt, "s", $param_term);
        
        // Set parameters
        $param_term = $_REQUEST["term"] . '%';
        
        // Attempt to execute the prepared statement
        if(mysqli_stmt_execute($stmt)){
            $result = mysqli_stmt_get_result($stmt);
            
            // Check number of rows in the result set
            if(mysqli_num_rows($result) > 0){
                // Fetch result rows as an associative array
                while($row = mysqli_fetch_array($result, MYSQLI_ASSOC)){
                    echo "<p>" . $row["name"] . "</p>";
                }
            } else{
                echo "<p>No matches found</p>";
            }
        } else{
            echo "ERROR: Could not able to execute $sql. " . mysqli_error($link);
        }
    }
     
    // Close statement
    mysqli_stmt_close($stmt);
}
 
// close connection
mysqli_close($link);
?>
```

The SQL [SELECT](http://www.bixiaguangnian.com/manual/sql/3393.html "SELECT") statement is used in combination with the [LIKE](http://www.bixiaguangnian.com/manual/sql/3411.html "LIKE") operator (line no-16) to find the matching records in countries database table. We've implemented the [prepared statement](http://www.bixiaguangnian.com/manual/php7/4005.html "prepared statement") for better search performance as well as to prevent the [SQL injection](http://www.bixiaguangnian.com/manual/sql/3422.html "SQL injection") attack.

<div class="callout callout-info mb-3">Note: Always filter and validate user input before using it in a SQL statement. You can also use PHP mysqli_real_escape_string() function to escape special characters in a user input and create a legal SQL string to protect against SQL injection.</div>