<?php
if(!$link = mysql_connect('mysql_host', 'mysql_user', 'mysql_password')) {
    exit('Could not connect to mysql');
}

if(!mysql_select_db('mysql_dbname', $link)) {
    exit('Could not select database');
}

$sql = 'SELECT * FROM foo';

$result = mysql_query($sql, $link);

if(!$result) {
    exit('DB Error, could not query the database\n'.mysql_error());
}

while($row = mysql_fetch_assoc($result)) {
    echo $row['foo'];
}

mysql_free_result($result); //Освобождаем память от результата запроса
?>