PHP MySQL Read Data
Read Data from MySQL Database
The SELECT statement is used to read data from a table:
SELECT column_name(s) FROM table_name
We can use the * sign to read all fields in the table:
SELECT * FROM table_name
To learn more about SQL, please visit ourSQL Tutorial。
Using MySQLi
In the following example, we read the id, firstname, and lastname columns from the MyGuests table in the myDB database and display them on the page:
Example (MySQLi - Object-oriented)
<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";
$conn = new mysqli($servername, $username, $password, $dbname);
if ($conn->connect_error) {
die("Connection failed:" . $conn->connect_error);
}
$sql = "SELECT id, firstname, lastname FROM MyGuests";
$result = $conn->query($sql);
if ($result->num_rows > 0) {
while($row = $result->fetch_assoc()) {
echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. " " . $row["lastname"]. "<br>";
}
} else {
echo "0 results";
}
$conn->close();
?>
The above code analysis is as follows:
First, we set the SQL statement to read the three fields id, firstname, and lastname from the MyGuests table. Then we use this SQL statement to retrieve the result set from the database and assign it to the variable $result.
The num_rows() function checks the returned data.
If multiple rows are returned, the fetch_assoc() function puts the result set into an associative array and outputs it in a loop. The while() loop iterates through the result set and outputs the values of the three fields id, firstname, and lastname.
The following example uses the MySQLi procedural approach, with similar effects to the code above:
Example (MySQLi - Procedural)
<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";
$conn = mysqli_connect($servername, $username, $password, $dbname);
if (!$conn) {
die("Connection failed:" . mysqli_connect_error());
}
$sql = "SELECT id, firstname, lastname FROM MyGuests";
$result = mysqli_query($conn, $sql);
if (mysqli_num_rows($result) > 0) {
while($row = mysqli_fetch_assoc($result)) {
echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. " " . $row["lastname"]. "<br>";
}
} else {
echo "0 results";
}
mysqli_close($conn);
?>
Using PDO (+ Prepared Statements)
The following example uses prepared statements.
It selects the id, firstname, and lastname fields from the MyGuests table and places them in an HTML 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();
$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>";
?>
Other extensions