Note, that if no connection is open, mysqli_real_escape_string() will return an empty string!
(PHP 5, PHP 7)
mysqli::real_escape_string -- mysqli_real_escape_string — Escapes special characters in a string for use in an SQL statement, taking into account the current charset of the connection
Object oriented style
$escapestr
)Procedural style
This function is used to create a legal SQL string that you can use in an SQL statement. The given string is encoded to an escaped SQL string, taking into account the current character set of the connection.
The character set must be set either at the server level, or with the API function mysqli_set_charset() for it to affect mysqli_real_escape_string(). See the concepts section on character sets for more information.
linkProcedural style only: A link identifier returned by mysqli_connect() or mysqli_init()
escapestrThe string to be escaped.
Characters encoded are NUL (ASCII 0), \n, \r, \, ', ", and Control-Z.
Returns an escaped string.
Example #1 mysqli::real_escape_string() example
Object oriented style
<?php
$mysqli = new mysqli("localhost", "my_user", "my_password", "world");
/* check connection */
if (mysqli_connect_errno()) {
printf("Connect failed: %s\n", mysqli_connect_error());
exit();
}
$mysqli->query("CREATE TEMPORARY TABLE myCity LIKE City");
$city = "'s Hertogenbosch";
/* this query will fail, cause we didn't escape $city */
if (!$mysqli->query("INSERT into myCity (Name) VALUES ('$city')")) {
printf("Error: %s\n", $mysqli->sqlstate);
}
$city = $mysqli->real_escape_string($city);
/* this query with escaped $city will work */
if ($mysqli->query("INSERT into myCity (Name) VALUES ('$city')")) {
printf("%d Row inserted.\n", $mysqli->affected_rows);
}
$mysqli->close();
?>
Procedural style
<?php
$link = mysqli_connect("localhost", "my_user", "my_password", "world");
/* check connection */
if (mysqli_connect_errno()) {
printf("Connect failed: %s\n", mysqli_connect_error());
exit();
}
mysqli_query($link, "CREATE TEMPORARY TABLE myCity LIKE City");
$city = "'s Hertogenbosch";
/* this query will fail, cause we didn't escape $city */
if (!mysqli_query($link, "INSERT into myCity (Name) VALUES ('$city')")) {
printf("Error: %s\n", mysqli_sqlstate($link));
}
$city = mysqli_real_escape_string($link, $city);
/* this query with escaped $city will work */
if (mysqli_query($link, "INSERT into myCity (Name) VALUES ('$city')")) {
printf("%d Row inserted.\n", mysqli_affected_rows($link));
}
mysqli_close($link);
?>
The above examples will output:
Error: 42000 1 Row inserted.
Note:
For those accustomed to using mysql_real_escape_string(), note that the arguments of mysqli_real_escape_string() differ from what mysql_real_escape_string() expects. The
linkidentifier comes first in mysqli_real_escape_string(), whereas the string to be escaped comes first in mysql_real_escape_string().
Note, that if no connection is open, mysqli_real_escape_string() will return an empty string!
You can avoid all character escaping issues (on the PHP side) if you use prepare() and bind_param(), as an alternative to placing arbitrary string values in SQL statements. This works because bound parameter values are NOT passed via the SQL statement syntax.
For percent sign and underscore I use this:
<?php
$more_escaped = addcslashes($escaped, '%_');
?>
When I submit data through Ajax I use a little function to reconvert the encoded chars to their original value. After that I do the escaping. Here the function:
function my_htmlentities($input){
$string = htmlentities($input,ENT_NOQUOTES,'UTF-8');
$string = str_replace('€',chr(128),$string);
$string = html_entity_decode($string,ENT_NOQUOTES,'ISO-8859-15');
return $string;
}
G.Zanferrari
If you wonder why (besides \, ' and ") NUL (ASCII 0), \n, \r, and Control-Z are escaped: it is not to prevent sql injection, but to prevent your sql logfile to get unreadable.
Note that this function will NOT escape _ (underscore) and % (percent) signs, which have special meanings in LIKE clauses.
As far as I know there is no function to do this, so you have to escape them yourself by adding a backslash in front of them.
if ($_SERVER['REQUEST_METHOD'] == "GET" && isset($_GET['value'])) {
$id = trim($link->real_escape_string($_GET['value']));
$sql = "DELETE FROM database WHERE IDItem = $id";
if (!$res = $link->query($sql)) {
$_SESSION['alertify'] = 'alertify.error("' . $link->error . '")';
} else {
$_SESSION['alertify'] = 'alertify.success("' . $value . ' was succesfully deleted")';
}
}
A PHP application I'm working on has many pages which (long story) need to share a PHP API that looks after a MySQL database. Easiest way was to have the app pages AJAX to the API .PHPs.
That means having the JavaScript of the AJAX encodeURIComponent(...) relevant bits of any data to be sent via HTTP POST and GET requests - space as %20 and so on.
But the SQL also needed real_escape_string(...) of the same data.
So I had the issue of whether to do the real_escape_string *before* or *after* encodeURIComponent? in other words in the application PHP or API PHP? Do either of the encodings mangle the other?
The real_escape_string would be "cleaner" in the API, both in principle, and because it needs an instance of mysqli class and there are are unlikely to be instances in the app.
(real_escape_string needs an instance because it's not a *static* function - I don't know why).
But I suspect that "in the API" is the mangle-avoiding place: the JavaScript encode gets undone by the HTTP call to whichever API element, then the element can safely real_escape_string what is to be put into the database.
Comments would be appreciated.
Note unlike PDO string escape, MySQLi does not include apostrophes.
So, you probably want something like this:
function escape($s){
$s = $this->mysqli->real_escape_string($s);
return "'$s'";
}