mysql_real_escape_string

    (PHP 4 >= 4.3.0, PHP 5)

    mysql_real_escape_string — Escapes special characters in a string for use in an SQL statement

    Aviso

    Esta extensão tornou-se defasada a partir do PHP 5.5.0 e foi removida no PHP 7.0.0. Em vez disso, as extensões MySQLi ou PDO_MySQL devem ser usadas. Veja também o guia MySQL: escolhendo uma API. Alternativas a esta função incluem:

    Descrição

    mysql_real_escape_string(string$unescaped_string, resource$link_identifier = NULL): string

    Escapes special characters in the unescaped_string, taking into account the current character set of the connection so that it is safe to place it in a mysql_query(). If binary data is to be inserted, this function must be used.

    mysql_real_escape_string() calls MySQL's library function mysql_real_escape_string, which prepends backslashes to the following characters: \x00, \n, \r, \, ', " and \x1a.

    This function must always (with few exceptions) be used to make data safe before sending a query to MySQL.

    Cuidado

    Security: the default character set

    The character set must be set either at the server level, or with the API function mysql_set_charset() for it to affect mysql_real_escape_string(). See the concepts section on character sets for more information.

    Parâmetros

    unescaped_string

    The string that is to be escaped.

    link_identifier

    A conexão MySQL. Se o identificador da conexão não for especificado, a última conexão aberta por mysql_connect() será usada. Se não houver uma conexão anterior, haverá uma tentativa de criar uma como se mysql_connect() tivesse sido chamada sem argumentos. Se nenhuma conexão for encontrada ou estabelecida, um erro de nível E_WARNING será gerado.

    Valor Retornado

    Returns the escaped string, or false on error.

    Erros/Exceções

    Executing this function without a MySQL connection present will also emit E_WARNING level PHP errors. Only execute this function with a valid MySQL connection present.

    Exemplos

    Exemplo #1 Simple mysql_real_escape_string() example

    <?php
    // Connect
    $link = mysql_connect('mysql_host', 'mysql_user', 'mysql_password')
    OR die(    mysql_error());

    // Query
    $query = sprintf("SELECT * FROM users WHERE user='%s' AND password='%s'",
    mysql_real_escape_string($user),
    mysql_real_escape_string($password));
    ?>

    Exemplo #2 mysql_real_escape_string() requires a connection example

    This example demonstrates what happens if a MySQL connection is not present when calling this function.

    <?php
    // We have not connected to MySQL

    $lastname = "O'Reilly";
    $_lastname = mysql_real_escape_string($lastname);

    $query = "SELECT * FROM actors WHERE last_name = '$_lastname'";

    var_dump($_lastname);
    var_dump($query);
    ?>

    O exemplo acima produzirá algo semelhante a:

    Warning: mysql_real_escape_string(): No such file or directory in /this/test/script.php on line 5 Warning: mysql_real_escape_string(): A link to the server could not be established in /this/test/script.php on line 5 bool(false) string(41) "SELECT * FROM actors WHERE last_name = ''"

    Exemplo #3 An example SQL Injection Attack

    <?php
    // We didn't check $_POST['password'], it could be anything the user wanted! For example:
    $_POST['username'] = 'aidan';
    $_POST['password'] = "' OR ''='";

    // Query database to check if there are any matching users
    $query = "SELECT * FROM users WHERE user='{$_POST['username']}' AND password='{$_POST['password']}'";
    mysql_query($query);

    // This means the query sent to MySQL would be:
    echo $query;
    ?>

    The query sent to MySQL: 

    SELECT * FROM users WHERE user='aidan' AND password='' OR ''=''

    This would allow anyone to log in without a valid password.

    Notas

    Nota:

    A MySQL connection is required before using mysql_real_escape_string() otherwise an error of level E_WARNING is generated, and false is returned. If link_identifier isn't defined, the last MySQL connection is used.

    Nota:

    If this function is not used to escape data, the query is vulnerable to SQL Injection Attacks.

    Nota: mysql_real_escape_string() does not escape % and _. These are wildcards in MySQL if combined with LIKE, GRANT, or REVOKE.

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