PHP MySQL reads data

from MySQL Database reads data

SELECT Statement is used to read data from a data table :

SELECT column_name(s) FROM table_name

We can use * Number to read all the fields in the data table ：

SELECT * FROM table_name

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Use MySQLi

In the following example, we start from myDB Database MyGuests Table read id, firstname and lastname Column and display it on the page ：

example (MySQLi - object-oriented )

<?php $servername = "localhost"; $username = "username"; $password = "password"; $dbname = "myDB"; // Create connection $conn = new mysqli($servername, $username, $password, $dbname); // Check connection if ($conn->connect_error) { die(" The connection fails : " . $conn->connect_error); } $sql = "SELECT id, firstname, lastname FROM MyGuests"; $result = $conn->query($sql); if ($result->num_rows > 0) { // Output data while($row = $result->fetch_assoc()) { echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. " " . $row["lastname"]. "<br>"; } } else { echo "0 result "; } $conn->close(); ?>

The above code is parsed as follows :

First , We set it up SQL Statements from MyGuests Read in data table id, firstname and lastname Three fields . Then we use this SQL Statement takes the result set from the database and assigns it to the copied variable $result.

function num_rows() Judge the returned data .

If multiple pieces of data are returned , function fetch_assoc() Put the associative set into the associative array and output circularly . while() Loop out the result set , And the output id, firstname and lastname Three field values .

The following example uses MySQLi Process oriented approach , The effect is similar to the above code :

example (MySQLi - Process oriented )

<?php $servername = "localhost"; $username = "username"; $password = "password"; $dbname = "myDB"; // Create connection $conn = mysqli_connect($servername, $username, $password, $dbname); // Check connection if (!$conn) { die(" The connection fails : " . mysqli_connect_error()); } $sql = "SELECT id, firstname, lastname FROM MyGuests"; $result = mysqli_query($conn, $sql); if (mysqli_num_rows($result) > 0) { // Output data while($row = mysqli_fetch_assoc($result)) { echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. " " . $row["lastname"]. "<br>"; } } else { echo "0 result "; } mysqli_close($conn); ?>

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Use PDO (+ Preprocessing )

The following example uses preprocessing statements .

Selected MyGuests In the table id, firstname and lastname Field , And on the HTML In the table ：

example (PDO)

<?php echo "<table style='border: solid 1px black;'>"; echo "<tr><th>Id</th><th>Firstname</th><th>Lastname</th></tr>"; class TableRows extends RecursiveIteratorIterator { function __construct($it) { parent::__construct($it, self::LEAVES_ONLY); } function current() { return "<td style='width:150px;border:1px solid black;'>" . parent::current(). "</td>"; } function beginChildren() { echo "<tr>"; } function endChildren() { echo "</tr>" . "\n"; } } $servername = "localhost"; $username = "username"; $password = "password"; $dbname = "myDBPDO"; try { $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password); $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); $stmt = $conn->prepare("SELECT id, firstname, lastname FROM MyGuests"); $stmt->execute(); // Set the result set to an associative array $result = $stmt->setFetchMode(PDO::FETCH_ASSOC); foreach(new TableRows(new RecursiveArrayIterator($stmt->fetchAll())) as $k=>$v) { echo $v; } } catch(PDOException $e) { echo "Error: " . $e->getMessage(); } $conn = null; echo "</table>"; ?>