php mysqli code example

Example 1: query php

<?php 
// MySqli connection
$mysqli = new mysqli("localhost", "my_username", "my_password", "my_database");

// Errors
if($mysqli->connect_error) {
  echo "<b>Failed to connect to MySQL: </b>" . $mysqli->connect_error;
}

// Query
$selectQuery = $mysqli->prepare("SELECT * FROM my_table");
$selectQuery->execute();
$selectQueryResult = $selectQuery->get_result();

// Loop 
while($selectQueryRow = $selectQueryResult->fetch_array()) {
  echo $selectQueryRow['my_column'];
}

// Example
$selectUsername = $mysqli->prepare("SELECT * FROM users");
$selectUsername->execute();
$selectUsernameResult = $selectUsername->get_result();
while($selectUsernameRow = $selectUsernameResult->fetch_array()) {
  echo $selectUsernameRow['username'];
}

Example 2: php mysql

In order to send data to a databse securely use prepared statements otherwise 
you can get attacked by an SQL Injection easily.
----
https://www.w3schools.com/php/php_mysql_prepared_statements.asp

Example 3: mysqli database

<?php
$mysqli = new mysqli("localhost", "my_user", "my_password", "test");

/* Vérification de la connexion */
if (mysqli_connect_errno()) {
    printf("Échec de la connexion : %s\n", mysqli_connect_error());
    exit();
}

/* Retourne le nom de la base de données courante */
if ($result = $mysqli->query("SELECT DATABASE()")) {
    $row = $result->fetch_row();
    printf("La base de données courante est %s.\n", $row[0]);
    $result->close();
}

/* Change la base de données en "world" */
$mysqli->select_db("world");

/* Retourne le nom de la base de données courante */
if ($result = $mysqli->query("SELECT DATABASE()")) {
    $row = $result->fetch_row();
    printf("La base de données courante est %s.\n", $row[0]);
    $result->close();
}

$mysqli->close();
?>