SQL

mysqli connect

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

// Check connection
if ($mysqli -> connect_errno) {

  echo "Failed to connect to MySQL: " . $mysqli -> connect_error;
  
  exit();

  }
?>

mysqli_connect php

<?php
$enlace = mysqli_connect("127.0.0.1", "mi_usuario", "mi_contraseña", "mi_bd");

if (!$enlace) {
    echo "Error: No se pudo conectar a MySQL." . PHP_EOL;
    echo "errno de depuración: " . mysqli_connect_errno() . PHP_EOL;
    echo "error de depuración: " . mysqli_connect_error() . PHP_EOL;
    exit;
}

echo "Éxito: Se realizó una conexión apropiada a MySQL! La base de datos mi_bd es genial." . PHP_EOL;
echo "Información del host: " . mysqli_get_host_info($enlace) . PHP_EOL;

mysqli_close($enlace);
?>

mysqli_connect

// mysqli_connect is an alias of mysqli::__construct()
$mysqli = new mysqli("host", "user", "password", "database", 'port', 'socket');

PHP mysqli_connect function

<?php;
$db_handle = mysqli_connect($db_server_name, $db_user_name, $db_password);
?>

mysqli_connect

$mysqli = new mysqli("localhost","my_user","my_password","my_db");