PHP正規表現を使用してHTMLタグを削除する方法

$str= preg_replace('/\s(?!src)[a-zA-Z]+=[\'\"]{1}[^\'\"]+[\'\"]{1}/iu',' $str);

$str = preg_replace('/\s(?!(src|alt))[a-zA-Z]+=[^\s]*/iu',' ', $str);

$str = preg_replace("/<([a-z]+)[^>]*>/i","",$str );

(\s)alt=[^\s]*

$search = array ("&#39;<script[^>]*?>.*?</script>&#39;si", // 去掉 javascript 
"&#39;<[\/\!]*?[^<>]*?>&#39;si", // 去掉 HTML 标记 
"&#39;([\r\n])[\s]+&#39;", // 去掉空白字符 
"&#39;&(quot|#34);&#39;i", // 替换 HTML 实体 
"&#39;&(amp|#38);&#39;i", 
"&#39;&(lt|#60);&#39;i", 
"&#39;&(gt|#62);&#39;i", 
"&#39;&(nbsp|#160);&#39;i" 
); // 作为 PHP 代码运行 
$replace = array ("","","\\1","\"","&","<",">"," "); 
$html = preg_replace($search, $replace, $html);