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
?>
Sanitize filters
| ID | Name | Flags | Description |
|---|---|---|---|
FILTER_SANITIZE_EMAIL |
"email" |
Remove all characters except letters, digits and
!#$%&'*+-=?^_`{|}~@.[].
|
|
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-encode string, optionally strip or encode special characters. |
FILTER_SANITIZE_MAGIC_QUOTES |
"magic_quotes" |
Apply addslashes().
(DEPRECATED as of PHP 7.3.0 and
REMOVED as of PHP 8.0.0,
use FILTER_SANITIZE_ADD_SLASHES instead.)
|
|
FILTER_SANITIZE_ADD_SLASHES |
"add_slashes" | Apply addslashes(). (Available as of PHP 7.3.0) | |
FILTER_SANITIZE_NUMBER_FLOAT |
"number_float" |
FILTER_FLAG_ALLOW_FRACTION,
FILTER_FLAG_ALLOW_THOUSAND,
FILTER_FLAG_ALLOW_SCIENTIFIC
|
Remove all characters except digits, +- and
optionally .,eE.
|
FILTER_SANITIZE_NUMBER_INT |
"number_int" | Remove all characters except digits, plus and minus sign. | |
FILTER_SANITIZE_SPECIAL_CHARS |
"special_chars" |
FILTER_FLAG_STRIP_LOW,
FILTER_FLAG_STRIP_HIGH,
FILTER_FLAG_STRIP_BACKTICK,
FILTER_FLAG_ENCODE_HIGH
|
HTML-encode '"<>& and characters with
ASCII value less than 32, optionally strip or encode other special
characters.
|
FILTER_SANITIZE_FULL_SPECIAL_CHARS |
"full_special_chars" |
FILTER_FLAG_NO_ENCODE_QUOTES
|
Equivalent to calling htmlspecialchars() with ENT_QUOTES set. Encoding quotes can
be disabled by setting FILTER_FLAG_NO_ENCODE_QUOTES. Like htmlspecialchars(), this
filter is aware of the default_charset and if a sequence of bytes is detected that
makes up an invalid character in the current character set then the entire string is rejected resulting in a 0-length string.
When using this filter as a default filter, see the warning below about setting the default flags to 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
|
Strip tags and HTML-encode double and single quotes, optionally strip
or encode special characters. Encoding quotes can be
disabled by setting FILTER_FLAG_NO_ENCODE_QUOTES.
(Deprecated as of PHP 8.1.0,
use htmlspecialchars() instead.)
|
FILTER_SANITIZE_STRIPPED |
"stripped" | Alias of "string" filter. (Deprecated as of PHP 8.1.0, use htmlspecialchars() instead.) | |
FILTER_SANITIZE_URL |
"url" |
Remove all characters except letters, digits and
$-_.+!*'(),{}|\\^~[]`<>#%";/?:@&=.
|
|
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
|
Do nothing, optionally strip or encode special characters. This
filter is also aliased to FILTER_DEFAULT.
|
Warning
When using one of these filters as a default filter either through your ini file
or through your web server's configuration, the default flags is set to
FILTER_FLAG_NO_ENCODE_QUOTES. You need to explicitly set
filter.default_flags to 0 to have quotes encoded by default. Like this:
Example #1 Configuring the default filter to act like htmlspecialchars
filter.default = full_special_chars
filter.default_flags = 0Changelog
| Version | Description |
|---|---|
| 8.1.0 |
FILTER_SANITIZE_STRING and
FILTER_SANITIZE_STRIPPED have been deprecated.
|
| 8.0.0 |
FILTER_SANITIZE_MAGIC_QUOTES has been removed.
|
| 7.3.0 |
FILTER_SANITIZE_ADD_SLASHES was added as a
replacement for FILTER_SANITIZE_MAGIC_QUOTES
|
| 7.3.0 |
FILTER_SANITIZE_MAGIC_QUOTES has been deprecated.
|
add a note
User Contributed Notes 16 notes
googlybash24 at aol dot com ¶
12 years ago
ipse at sergiosantos dot me ¶
4 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 ¶
15 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 ¶
1 year 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 ¶
6 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.
