Replace all occurrences of a string in DB

Searches and replaces all of occurrences 

of a string in all tables and all fields of the given Database.

<?php
/**
* @kudos http://stackoverflow.com/a/10182498
*/
 
header("Content-Type: text/plain");

$host = "localhost";
$username = "root";
$password = "";
$database = "mydatabase";
$string_to_replace  = 'old.example.com';
$new_string = 'new.example.com';

// Connect to database server
mysql_connect($host, $username, $password);

// Select database
mysql_select_db($database);

// List all tables in database
$sql = "SHOW TABLES FROM ".$database;
$tables_result = mysql_query($sql);

if (!$tables_result) {
    echo "Database error, could not list tables\nMySQL error: " . mysql_error();
    exit;
}

echo "In these fields '$string_to_replace' have been replaced with '$new_string'\n\n";
while ($table = mysql_fetch_row($tables_result)) {
    echo "Table: {$table[0]}\n";
    $fields_result = mysql_query("SHOW COLUMNS FROM ".$table[0]);
    if (!$fields_result) {
        echo 'Could not run query: ' . mysql_error();
        exit;
    }
    if (mysql_num_rows($fields_result) > 0) {
        while ($field = mysql_fetch_assoc($fields_result)) {
            if (stripos($field['Type'], "VARCHAR") !== false || stripos($field['Type'], "TEXT") !== false) {
                echo "  ".$field['Field']."\n";
                $sql = "UPDATE ".$table[0]." SET ".$field['Field']." = replace(".$field['Field'].", '$string_to_replace', '$new_string')";
                mysql_query($sql);
            }
        }
        echo "\n";
    }
}

mysql_free_result($tables_result);