Remember to trim() the $_POST before your filters are applied:
<?php
// We trim the $_POST data before any spaces get encoded to "%20"
// Trim array values using this function "trim_value"
function trim_value(&$value)
{
$value = trim($value); // this removes whitespace and related characters from the beginning and end of the string
}
array_filter($_POST, 'trim_value'); // the data in $_POST is trimmed
$postfilter = // set up the filters to be used with the trimmed post array
array(
'user_tasks' => array('filter' => FILTER_SANITIZE_STRING, 'flags' => !FILTER_FLAG_STRIP_LOW), // removes tags. formatting code is encoded -- add nl2br() when displaying
'username' => array('filter' => FILTER_SANITIZE_ENCODED, 'flags' => FILTER_FLAG_STRIP_LOW), // we are using this in the url
'mod_title' => array('filter' => FILTER_SANITIZE_ENCODED, 'flags' => FILTER_FLAG_STRIP_LOW), // we are using this in the url
);
$revised_post_array = filter_var_array($_POST, $postfilter); // must be referenced via a variable which is now an array that takes the place of $_POST[]
echo (nl2br($revised_post_array['user_tasks'])); //-- use nl2br() upon output like so, for the ['user_tasks'] array value so that the newlines are formatted, since this is our HTML <textarea> field and we want to maintain newlines
?>
Filter für die Bereinigung
| ID | Name | Flags | Description |
|---|---|---|---|
FILTER_SANITIZE_EMAIL |
"email" |
Entfernt alle Zeichen außer Buchstaben, Ziffern und
!#$%&'*+-=?^_`{|}~@.[].
|
|
FILTER_SANITIZE_ENCODED |
"encoded" |
FILTER_FLAG_STRIP_LOW,
FILTER_FLAG_STRIP_HIGH,
FILTER_FLAG_STRIP_BACKTICK,
FILTER_FLAG_ENCODE_LOW,
FILTER_FLAG_ENCODE_HIGH
|
URL-Kodierung von Zeichenketten, optionales Entfernen oder Kodieren von Sonderzeichen. |
FILTER_SANITIZE_MAGIC_QUOTES |
"magic_quotes" |
Wendet addslashes() an. (Ab PHP 7.3.0
VERALTET und ab PHP 8.0.0
ENTFERNT. Verwenden Sie stattdessen
FILTER_SANITIZE_ADD_SLASHES.)
|
|
FILTER_SANITIZE_ADD_SLASHES |
"add_slashes" | Wendet addslashes() an. (Verfügbar ab PHP 7.3.0) | |
FILTER_SANITIZE_NUMBER_FLOAT |
"number_float" |
FILTER_FLAG_ALLOW_FRACTION,
FILTER_FLAG_ALLOW_THOUSAND,
FILTER_FLAG_ALLOW_SCIENTIFIC
|
Entfernt alle Zeichen außer Ziffern, +- und
optional .,eE.
|
FILTER_SANITIZE_NUMBER_INT |
"number_int" | Entfernt alle Zeichen außer Ziffern, Plus- und Minuszeichen. | |
FILTER_SANITIZE_SPECIAL_CHARS |
"special_chars" |
FILTER_FLAG_STRIP_LOW,
FILTER_FLAG_STRIP_HIGH,
FILTER_FLAG_STRIP_BACKTICK,
FILTER_FLAG_ENCODE_HIGH
|
HTML-Kodierung von '"<>& und Zeichen mit
ASCII-Wert kleiner als 32, optional Entfernen oder Kodieren anderer
Sonderzeichen
|
FILTER_SANITIZE_FULL_SPECIAL_CHARS |
"full_special_chars" |
FILTER_FLAG_NO_ENCODE_QUOTES
|
Äquivalent zum Aufruf von htmlspecialchars(), bei
dem ENT_QUOTES gesetzt ist. Die Kodierung von
Anführungszeichen kann durch Setzen von
FILTER_FLAG_NO_ENCODE_QUOTES deaktiviert werden.
Wie htmlspecialchars() kennt dieser Filter die
Einstellung default_charset
und wenn eine Folge von Bytes entdeckt wird, die ein im aktuellen
Zeichensatz ungültiges Zeichen enthält, dann wird die komplette
Zeichenkette verworfen, was zu einer Zeichenkette der Länge 0 führt.
Wenn dieser Filter als Standardfilter verwendet wird, siehe die
Warnung unten über das Setzen der Standardflags auf 0.
|
FILTER_SANITIZE_STRING |
"string" |
FILTER_FLAG_NO_ENCODE_QUOTES,
FILTER_FLAG_STRIP_LOW,
FILTER_FLAG_STRIP_HIGH,
FILTER_FLAG_STRIP_BACKTICK,
FILTER_FLAG_ENCODE_LOW,
FILTER_FLAG_ENCODE_HIGH,
FILTER_FLAG_ENCODE_AMP
|
Entfernt Tags und HTML-kodiert doppelte und einfache
Anführungszeichen und entfernt oder kodiert optional Sonderzeichen.
Die Kodierung von Anführungszeichen kann durch Setzen von
FILTER_FLAG_NO_ENCODE_QUOTES deaktiviert werden.
(Seit PHP 8.1.0 veraltet, stattdessen sollte
htmlspecialchars() verwendet werden.)
|
FILTER_SANITIZE_STRIPPED |
"stripped" | Alias des "String"-Filters. (Seit PHP 8.1.0 veraltet, stattdessen sollte htmlspecialchars() verwendet werden.) | |
FILTER_SANITIZE_URL |
"url" |
Entfernt alle Zeichen außer Buchstaben, Ziffern und
$-_.+!*'(),{}|\\^~[]`<>#%";/?:@&=.
|
|
FILTER_UNSAFE_RAW |
"unsafe_raw" |
FILTER_FLAG_STRIP_LOW,
FILTER_FLAG_STRIP_HIGH,
FILTER_FLAG_STRIP_BACKTICK,
FILTER_FLAG_ENCODE_LOW,
FILTER_FLAG_ENCODE_HIGH,
FILTER_FLAG_ENCODE_AMP
|
Tut nichts oder entfernt oder kodiert optional Sonderzeichen. Dieser
Filter ist auch ein Alias für FILTER_DEFAULT.
|
Warnung
Wenn einer dieser Filter als Standardfilter verwendet wird, entweder durch
die ini-Datei oder über die Konfiguration des Webservers, wird das
Standardflag auf FILTER_FLAG_NO_ENCODE_QUOTES
gesetzt. Damit Anführungszeichen standardmäßig kodiert werden, muss
filter.default_flags explizit auf 0 gesetzt werden. Etwa so:
Beispiel #1 Den Standardfilter so konfigurieren, dass er sich wie htmlspecialchars verhält
filter.default = full_special_chars
filter.default_flags = 0Changelog
| Version | Beschreibung |
|---|---|
| 8.1.0 |
FILTER_SANITIZE_STRING und
FILTER_SANITIZE_STRIPPED werden als veraltet
eingestuft.
|
| 8.0.0 |
FILTER_SANITIZE_MAGIC_QUOTES wurde entfernt.
|
| 7.3.0 |
FILTER_SANITIZE_ADD_SLASHES wurde als Ersatz für
FILTER_SANITIZE_MAGIC_QUOTES hinzugefügt.
|
| 7.3.0 |
FILTER_SANITIZE_MAGIC_QUOTES wird als veraltet
eingestuft.
|
add a note
User Contributed Notes 16 notes
googlybash24 at aol dot com ¶
12 years ago
ipse at sergiosantos dot me ¶
3 years ago
Although it's specifically mentioned in the above documentation, because many seem to find this unintuitive it's worth pointing out that FILTER_SANITIZE_NUMBER_FLOAT will remove the decimal character unless you specify FILTER_FLAG_ALLOW_FRACTION:
<?php
$number_string = '12.34';
echo filter_var( $number_string, FILTER_SANITIZE_NUMBER_FLOAT ); // 1234
echo filter_var( $number_string, FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_FRACTION ); // 12.34
?>
Anonymous ¶
9 years ago
FILTER_SANITIZE_STRING doesn't behavior the same as strip_tags function. strip_tags allows less than symbol inferred from context, FILTER_SANITIZE_STRING strips regardless.
<?php
$smaller = "not a tag < 5";
echo strip_tags($smaller); // -> not a tag < 5
echo filter_var ( $smaller, FILTER_SANITIZE_STRING); // -> not a tag
?>
Willscrlt ¶
8 years ago
To include multiple flags, simply separate the flags with vertical pipe symbols.
For example, if you want to use filter_var() to sanitize $string with FILTER_SANITIZE_STRING and pass in FILTER_FLAG_STRIP_HIGH and FILTER_FLAG_STRIP_LOW, just call it like this:
$string = filter_var($string, FILTER_SANITIZE_STRING, FILTER_FLAG_STRIP_HIGH | FILTER_FLAG_STRIP_LOW);
The same goes for passing a flags field in an options array in the case of using callbacks.
$var = filter_var($string, FILTER_SANITIZE_SPECIAL_CHARS,
array('flags' => FILTER_FLAG_STRIP_LOW | FILTER_FLAG_ENCODE_HIGH));
Thanks to the Brain Goo blog at popmartian.com/tipsntricks/for this info.
AntonioPrimera ¶
8 years ago
Please be aware that when using filter_var() with FILTER_SANITIZE_NUMBER_FLOAT and FILTER_SANITIZE_NUMBER_INT the result will be a string, even if the input value is actually a float or an int.
Use FILTER_VALIDATE_FLOAT and FILTER_VALIDATE_INT, which will convert the result to the expected type.
marcus at synchromedia dot co dot uk ¶
14 years ago
It's not entirely clear what the LOW and HIGH ranges are. LOW is characters below 32, HIGH is those above 127, i.e. outside the ASCII range.
<?php
$a = "\tcafé\n";
//This will remove the tab and the line break
echo filter_var($a, FILTER_SANITIZE_STRING, FILTER_FLAG_STRIP_LOW);
//This will remove the é.
echo filter_var($a, FILTER_SANITIZE_STRING, FILTER_FLAG_STRIP_HIGH);
?>
galvao at galvao dot eti dot br ¶
11 years ago
Just to clarify, since this may be unknown for a lot of people:
ASCII characters above 127 are known as "Extended" and they represent characters such as greek letters and accented letters in latin alphabets, used in languages such as pt_BR.
A good ASCII quick reference (aside from the already mentioned Wikipedia article) can be found at: http://www.asciicodes.com/
david dot drakulovski at gmail dot com ¶
10 years ago
Here is a simpler and a better presented ASCII list for the <32 or 127> filters
(if wikipedia confused the hell out of you):
http://www.danshort.com/ASCIImap/
finkenb2 at msu dot edu ¶
10 months ago
With the deprecation of FILTER_SANITIZE_STRING, the "use htmlspecialchars instead" is an incomplete comment. The functionality of FILTER_SANITIZE_STRING was a combination of htmlspcialchars and (approximately) strip_tags. For true compatibility a polyfil may be needed:
<?php
function filter_string_polyfill(string $string): string
{
$str = preg_replace('/\x00|<[^>]*>?/', '', $string);
return str_replace(["'", '"'], [''', '"'], $str);
}
$string = "Some \"' <bizzare> string & to Sanitize < !$@%";
echo filter_var($string,FILTER_SANITIZE_STRING).PHP_EOL;
//Some "' string & to Sanitize
echo htmlspecialchars($string).PHP_EOL;
//Some "' <bizzare> string & to Sanitize < !$@%
echo strip_tags($string).PHP_EOL;
//Some "' string & to Sanitize < !$@%
echo htmlspecialchars(strip_tags($string,ENT_QUOTES)).PHP_EOL;
//Some "' string & to Sanitize < !$@%
echo filter_string_polyfill($string).PHP_EOL;
//Some "' string & to Sanitize
darren at daz-web dot com ¶
5 years ago
For those looking for a simple way around filtering POST forms that have textarea elements in them. If you also need tab for example you can extend quite easily.
<?php
//create an array of all relevant textareas
$textareas = array("ta1");
foreach($_POST as $k => $v)
{
$v = trim($v);//so we are sure it is whitespace free at both ends
//preserve newline for textarea answers
if(in_array($k,$textareas))$v=str_replace("\n","[NEWLINE]",$v);
//sanitise string
$v = filter_var($v, FILTER_SANITIZE_STRING, FILTER_FLAG_STRIP_LOW | FILTER_FLAG_STRIP_HIGH | FILTER_FLAG_STRIP_BACKTICK);
//now replace the placeholder with the original newline
$_POST[$k] = str_replace("[NEWLINE]","\n",$v);
}
//simple form for testing submital
?><!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>Filter test</title>
</head>
<body>
<form action="" method="post">
<p>
<textarea name="ta1" cols="30" rows="10"><?php echo $_POST['ta1']; ?></textarea>
</p>
<p>
<input type="text" name="txt1" size="30" value="<?php echo $_POST['txt1']; ?>" />
</p>
<p>
<input type="submit" />
</p>
</form>
</body>
</html>
adellemfrank at hotmail dot com ¶
12 years ago
A good list of which ASCII characters are < 32 and > 127 can be found at: http://en.wikipedia.org/wiki/ASCII#ASCII_printable_characters
Rodrigo Guariento ¶
4 years ago
To get ONLY numbers from a string use this code:
echo preg_replace('/[^0-9]/', '', '123456-789');
anonymous ¶
4 years ago
In the "FILTER_SANITIZE_URL" section where it says, "Remove all characters except letters, digits and $-_.+!*'(),{}|\\^~[]`<>#%";/?:@&=." is there a reason why there is a double backslash (\\)? Shouldn't there only be one backslash if it's saying that backslashes are allowed?
Anonymous ¶
4 years ago
<?php
/*
filter all ascii and save juste 0-9 a-Z and @ . _
*/
echo alphanum('abcdefghABCDEFGH0123456789/!:;@._');
// return abcdefghABCDEFGH0123456789@._
function alphanum( $string , $x=''){
$h=strlen($string);
for($a=0; $a<$h; $a++) {
$i = ord($string[$a]);
if(
($i==46) || // .
($i==64) || // @
($i==95) || // _
($i > 47 && $i < 58) || //0123456789
($i > 64 && $i < 91) || //ABCDEFGH..Z
($i > 96 && $i < 123) //abcdefgh..z
) { $x .= $string[$a]; }
}
return $x;
}
?>
Dmitry Snytkine ¶
13 years ago
Beware that FILTER_FLAG_STRIP_LOW strips NEWLINE and TAG and CARRIAGE RETURN chars. If you have a form that accepts user input in plaintext format, all the submitted text will lose all the line breaks, making it appear all on one line. This basically renders this filter useless for parsing user-submitted text, even in plain text.
