wp_kses() – Function | Developer.WordPress.org

Filters text content and strips out disallowed HTML.

Description

This function makes sure that only the allowed HTML element names, attribute names, attribute values, and HTML entities will occur in the given text string.

This function expects unslashed data.

Parameters

$contentstringrequired: Text content to filter.
$allowed_htmlarray[]|stringrequired: An array of allowed HTML elements and attributes, or a context name such as 'post'. See wp_kses_allowed_html() for the list of accepted context names.
$allowed_protocolsstring[]optional: Array of allowed URL protocols.
Defaults to the result of wp_allowed_protocols() .
Default:array()

Return

string Filtered content containing only the allowed HTML.

More Information

KSES is a recursive acronym which stands for “KSES Strips Evil Scripts”.

For parameter $allowed_protocols, the default allowed protocols are http, https, ftp, mailto, news, irc, gopher, nntp, feed, and telnet. This covers all common link protocols, except for javascript, which should not be allowed for untrusted users.

Source

function wp_kses( $content, $allowed_html, $allowed_protocols = array() ) {
	if ( empty( $allowed_protocols ) ) {
		$allowed_protocols = wp_allowed_protocols();
	}

	$content = wp_kses_no_null( $content, array( 'slash_zero' => 'keep' ) );
	$content = wp_kses_normalize_entities( $content );
	$content = wp_kses_hook( $content, $allowed_html, $allowed_protocols );

	return wp_kses_split( $content, $allowed_html, $allowed_protocols );
}

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Changelog

Version	Description
1.0.0	Introduced.

User Contributed Notes

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Bart Kuijper 5 years ago

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Many function names in WordPress are self-explanatory and if they aren’t, their documentation usually sheds some light on how they got their name. I find this makes it easier to later recall their names and uses. However, wp_kses is an exception. So for anyone else wondering:

kses comes from the terms XSS (cross-site scripting) and access. It’s also a recursive acronym (every open-source project should have one!) for “kses strips evil scripts”.

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Codex 10 years ago

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Allowed HTML tags array
This is an example of how to format an array of allowed HTML tags and attributes.
```
array(
    'a' => array(
        'href' => array(),
        'title' => array()
    ),
    'br' => array(),
    'em' => array(),
    'strong' => array(),
);
```
- From what is shown in the core code, the attributes are typically set to true, rather than array(), so more like this: array( 'a' => array( 'href' => true, 'title' => true, ), 'br' => array(), 'em' => array(), 'strong' => array(), );
  
  nosilver4u 4 years ago
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Abdul Hadi 4 years ago

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WordPress wp_kses is an HTML filtering mechanism. If you need to escape your output in a specific (custom) way, wp_kses function in WordPress will come handy.
```
<?php
$str = 'Check Kses function I am <strong>stronger</strong> and cooler every single day <a href="#" rel="nofollow ugc">Click Here</a>';
echo $str;
$arr = array( 'br' => array(), 'p' => array(), 'strong' => array() );
echo 'String using wp_kses function....' . wp_kses( $str, $arr );
?>
```
Output:
Before wp_kses: Check Kses function I am stronger and cooler every single day Click Here
After wp_kses: String using wp_kses function…. Check Kses function I am stronger and cooler every single day Click Here

It will display a resultant string as shown in the output screen. It only reflects the allowed tags strong, br, p as defined in wp_kses function and anchor tag is removed. So, no link for click Here text is formed.
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J.D. Grimes 10 years ago

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See wp_kses_allowed_html() and /wp-includes/kses.php to get a list of the possible default values of the allowed HTML tags.

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TomS Caprice 3 years ago

// Allowed img tag and support svg base64 data like:  <img src="data:image/svg+xml;base64,__base64_code__" />
function wpdocs_allowed_html() {
	return array(
		'img' => array(
			'title' => array(),
			'src'	=> array(),
			'alt'	=> array(),
		)
	);
}

function wpdocs_allowed_protocols() {
	return array(
		'data' 	=> array(),
		'http'	=> array(),
		'https' => array(),
	);
}

function wpdocs_output_img() {
	$html = '';
	ob_start();
	?>

	<img src="data:image/svg+xml;base64,Your_base64_code" title="img_title" alt="alt_info" />

	<?php 
	$html = ob_get_contents();
	ob_end_clean();
	return $html;
}

$allowed_html      = wpdocs_allowed_html();
$allowed_protocols = wpdocs_allowed_protocols();
$wpdocs_img        = wpdocs_output_img();

echo wp_kses( $wpdocs_img, $allowed_html, $allowed_protocols )

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Rene Hermenau 2 years ago

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If you want to keep certain style properties you have to use another filter.
Unortunately wp_kses will check the style properties against a list of allowed properties and it will still strip the style attribute if none of the styles are safe.

E.g. Use this filter if you want to keep the `display` property within a `style`:
a
```
add_filter( 'safe_style_css', function( $styles ) {
    $styles[] = 'display';
    return $styles;
} );
```
Check kses.php for default:
https://core.trac.wordpress.org/browser/trunk/src/wp-includes/kses.php
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Mahdi Yazdani 2 years ago

Sanitize SVG markup for front-end display using wp_kses, and a list of allowed HTML elements and attributes specific to a SVG tag.

/**
* Sanitize SVG markup for front-end display.
*
* @param  string $svg SVG markup to sanitize.
* @return string 	  Sanitized markup.
*/
function prefix_sanitize_svg( $svg = '' ) {
	$allowed_html = [
		'svg'  => [
			'xmlns'       => [],
			'fill'        => [],
			'viewbox'     => [],
			'role'        => [],
			'aria-hidden' => [],
			'focusable'   => [],
			'height'      => [],
			'width'       => [],
		],
		'path' => [
			'd'    => [],
			'fill' => [],
		],
	];

	return wp_kses( $svg, $allowed_html );
}

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BigupJeff 2 years ago

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If you are using wp_kses to escape SVG, be warned `wp_kses() ` will strip camelcased attributes in your args. Make sure your args are converted to lowercase for their uppercase equivalents. For example:
```
$args = array(
	'svg'            => array(
		'viewbox'             => true, // viewBox
		'preserveaspectratio' => true, // preserveAspectRatio
	),
	'lineargradient' => array(             // linearGradient
		'gradientunits'     => true,   // gradientUnits
		'gradienttransform' => true,   // gradientTransform
		'spreadmethod'      => true,   // spreadMethod
	),
);
```
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Aurovrata Venet 1 year ago

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Allowed HTML elements attributes don’t need to be empty arrays, but simply a boolean,
```
array(
    'a' => array(
        'href' => true,
        'title' => true
    ),
    'br' => array(),
    'em' => array(),
    'strong' => array(),
);
```
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wp_kses( string $content, array[]|string $allowed_html, string[] $allowed_protocols = array() ): string

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