wp_kses_hair( string $attr, string[] $allowed_protocols )

从包含属性的字符串生成属性列表。
Builds an attribute list from string containing attributes.

说明（Description）

这个函数做了很多工作。它将一个属性列表解析成一个包含属性数据的数组，并尝试做正确的事情，即使它得到奇怪的输入。它将在属性值周围添加引号，这些属性值周围没有任何引号或撇号，以便更容易地生成符合W3C的HTML规范的HTML代码。它还将从属性值中删除错误的URL协议。它还通过使用首先定义的属性（foo='bar'foo='baz'将导致foo='bar'），减少重复属性。

参数（Parameters）

源码（Source）

/**
 * Builds an attribute list from string containing attributes.
 *
 * This function does a lot of work. It parses an attribute list into an array
 * with attribute data, and tries to do the right thing even if it gets weird
 * input. It will add quotes around attribute values that don't have any quotes
 * or apostrophes around them, to make it easier to produce HTML code that will
 * conform to W3C's HTML specification. It will also remove bad URL protocols
 * from attribute values. It also reduces duplicate attributes by using the
 * attribute defined first (foo='bar' foo='baz' will result in foo='bar').
 *
 * @since 1.0.0
 *
 * @param string $attr              Attribute list from HTML element to closing HTML element tag
 * @param array  $allowed_protocols Allowed protocols to keep
 * @return array List of attributes after parsing
 */
function wp_kses_hair($attr, $allowed_protocols) {
	$attrarr = array();
	$mode = 0;
	$attrname = '';
	$uris = array('xmlns', 'profile', 'href', 'src', 'cite', 'classid', 'codebase', 'data', 'usemap', 'longdesc', 'action');

	// Loop through the whole attribute list

	while (strlen($attr) != 0) {
		$working = 0; // Was the last operation successful?

		switch ($mode) {
			case 0 : // attribute name, href for instance

				if ( preg_match('/^([-a-zA-Z:]+)/', $attr, $match ) ) {
					$attrname = $match[1];
					$working = $mode = 1;
					$attr = preg_replace( '/^[-a-zA-Z:]+/', '', $attr );
				}

				break;

			case 1 : // equals sign or valueless ("selected")

				if (preg_match('/^s*=s*/', $attr)) // equals sign
					{
					$working = 1;
					$mode = 2;
					$attr = preg_replace('/^s*=s*/', '', $attr);
					break;
				}

				if (preg_match('/^s+/', $attr)) // valueless
					{
					$working = 1;
					$mode = 0;
					if(false === array_key_exists($attrname, $attrarr)) {
						$attrarr[$attrname] = array ('name' => $attrname, 'value' => '', 'whole' => $attrname, 'vless' => 'y');
					}
					$attr = preg_replace('/^s+/', '', $attr);
				}

				break;

			case 2 : // attribute value, a URL after href= for instance

				if (preg_match('%^"([^"]*)"(s+|/?$)%', $attr, $match))
					// "value"
					{
					$thisval = $match[1];
					if ( in_array(strtolower($attrname), $uris) )
						$thisval = wp_kses_bad_protocol($thisval, $allowed_protocols);

					if(false === array_key_exists($attrname, $attrarr)) {
						$attrarr[$attrname] = array ('name' => $attrname, 'value' => $thisval, 'whole' => "$attrname="$thisval"", 'vless' => 'n');
					}
					$working = 1;
					$mode = 0;
					$attr = preg_replace('/^"[^"]*"(s+|$)/', '', $attr);
					break;
				}

				if (preg_match("%^'([^']*)'(s+|/?$)%", $attr, $match))
					// 'value'
					{
					$thisval = $match[1];
					if ( in_array(strtolower($attrname), $uris) )
						$thisval = wp_kses_bad_protocol($thisval, $allowed_protocols);

					if(false === array_key_exists($attrname, $attrarr)) {
						$attrarr[$attrname] = array ('name' => $attrname, 'value' => $thisval, 'whole' => "$attrname='$thisval'", 'vless' => 'n');
					}
					$working = 1;
					$mode = 0;
					$attr = preg_replace("/^'[^']*'(s+|$)/", '', $attr);
					break;
				}

				if (preg_match("%^([^s"']+)(s+|/?$)%", $attr, $match))
					// value
					{
					$thisval = $match[1];
					if ( in_array(strtolower($attrname), $uris) )
						$thisval = wp_kses_bad_protocol($thisval, $allowed_protocols);

					if(false === array_key_exists($attrname, $attrarr)) {
						$attrarr[$attrname] = array ('name' => $attrname, 'value' => $thisval, 'whole' => "$attrname="$thisval"", 'vless' => 'n');
					}
					// We add quotes to conform to W3C's HTML spec.
					$working = 1;
					$mode = 0;
					$attr = preg_replace("%^[^s"']+(s+|$)%", '', $attr);
				}

				break;
		} // switch

		if ($working == 0) // not well formed, remove and try again
		{
			$attr = wp_kses_html_error($attr);
			$mode = 0;
		}
	} // while

	if ($mode == 1 && false === array_key_exists($attrname, $attrarr))
		// special case, for when the attribute list ends with a valueless
		// attribute like "selected"
		$attrarr[$attrname] = array ('name' => $attrname, 'value' => '', 'whole' => $attrname, 'vless' => 'y');

	return $attrarr;
}