str_replace(find,replace,string,count)

echo str_replace(array("m","i"),array("n","z"),"my name is jim!")

echo str_replace(array('m','i'),'n',"my name is jim!");

$vowels = array("a", "e", "i", "o", "u", "A", "E", "I", "O", "U");

$onlyconsonants = str_replace($vowels, "","Hello World of PHP");
echo $onlyconsonants;

   <"','&quot;',$string);
    $string = str_replace("'",'',$string);
    $string = str_replace('"','',$string);
    $string = str_replace(';','',$string);
    $string = str_replace('<','&lt;',$string);
    $string = str_replace('>','&gt;',$string);
    $string = str_replace("{",'',$string);
    $string = str_replace('}','',$string);
    $string = str_replace('','',$string);
    return $string;
    }
    "#script:#i", "ｓｃｒｉｐｔ：", $str);
    $str = preg_replace("#<[/]{0,1}(link|meta|ifr|fra|scr)[^>]*>#isU", '', $str);
    $str = preg_replace("#[ ]{1,}#", ' ', $str);
    return $str;
    }else if($safestep == 2){
    $str = addslashes(htmlspecialchars(stripslashes($str)));
    $str = preg_replace("#eval#i", 'ｅｖａｌ', $str);
    $str = preg_replace("#union#i", 'ｕｎｉｏｎ', $str);
    $str = preg_replace("#concat#i", 'ｃｏｎｃａｔ', $str);
    $str = preg_replace("#--#", '－－', $str);
    $str = preg_replace("#[ ]{1,}#", ' ', $str);
    return $str;
    }else{
    return $str;
    }
    }
    "|')([^2=[]]+)2([^[]]*])/i',$text,$mat)){
               $text=str_replace($mat[0],$mat[1].'|'.$mat[3].'|'.$mat[4],$text);
           }
           //空属性转换
           $text =  str_replace('''','||',$text);
           $text = str_replace('""','||',$text);
           //过滤错误的单个引号
           while(preg_match('/[[^[]]*("|')[^[]]*]/i',$text,$mat)){
               $text=str_replace($mat[0],str_replace($mat[1],'',$mat[0]),$text);
           }
           //转换其它所有不合法的 < >
           $text =  str_replace('<','&lt;',$text);
           $text = str_replace('>','&gt;',$text);
           $text = str_replace('"','&quot;',$text);
           //反转换
           $text =  str_replace('[','<',$text);
           $text =  str_replace(']','>',$text);
           $text =  str_replace('|','"',$text);
           //过滤多余空格
           $text =  str_replace('  ',' ',$text);
           return $text;
       }
    ";:?+/={}[]-_|''; 
       for ($i = 0; $i < strlen($search); $i++) { 
           // ;? matches the ;, which is optional 
           // 0{0,7} matches any padded zeros, which are optional and go up to 8 chars 
           // @ @ search for the hex values 
           $val = preg_replace('/(&#[xX]0{0,8}'.dechex(ord($search[$i])).';?)/i', $search[$i], $val);//with a ; 
           // @ @ 0{0,7} matches '0' zero to seven times 
           $val = preg_replace('/(&#0{0,8}'.ord($search[$i]).';?)/', $search[$i], $val); // with a ; 
       } 
       // now the only remaining whitespace attacks are , , and  
       $ra1 = Array('javascript', 'vbscript', 'expression', 'applet', 'meta', 'xml', 'blink', 'link', 'style', 'script', 'embed', 'object', 'iframe', 'frame', 'frameset', 'ilayer', 'layer', 'bgsound', 'title', 'base'); 
       $ra2 = Array('onabort', 'onactivate', 'onafterprint', 'onafterupdate', 'onbeforeactivate', 'onbeforecopy', 'onbeforecut', 'onbeforedeactivate', 'onbeforeeditfocus', 'onbeforepaste', 'onbeforeprint', 'onbeforeunload', 'onbeforeupdate', 'onblur', 'onbounce', 'oncellchange', 'onchange', 'onclick', 'oncontextmenu', 'oncontrolselect', 'oncopy', 'oncut', 'ondataavailable', 'ondatasetchanged', 'ondatasetcomplete', 'ondblclick', 'ondeactivate', 'ondrag', 'ondragend', 'ondragenter', 'ondragleave', 'ondragover', 'ondragstart', 'ondrop', 'onerror', 'onerrorupdate', 'onfilterchange', 'onfinish', 'onfocus', 'onfocusin', 'onfocusout', 'onhelp', 'onkeydown', 'onkeypress', 'onkeyup', 'onlayoutcomplete', 'onload', 'onlosecapture', 'onmousedown', 'onmouseenter', 'onmouseleave', 'onmousemove', 'onmouseout', 'onmouseover', 'onmouseup', 'onmousewheel', 'onmove', 'onmoveend', 'onmovestart', 'onpaste', 'onpropertychange', 'onreadystatechange', 'onreset', 'onresize', 'onresizeend', 'onresizestart', 'onrowenter', 'onrowexit', 'onrowsdelete', 'onrowsinserted', 'onscroll', 'onselect', 'onselectionchange', 'onselectstart', 'onstart', 'onstop', 'onsubmit', 'onunload'); 
       $ra = array_merge($ra1, $ra2); 
       $found = true; // keep replacing as long as the previous round replaced something 
       while ($found == true) { 
           $val_before = $val; 
           for ($i = 0; $i < sizeof($ra); $i++) { 
               $pattern = '/'; 
               for ($j = 0; $j < strlen($ra[$i]); $j++) { 
                   if ($j > 0) { 
                       $pattern .= '('; 
                       $pattern .= '(&#[xX]0{0,8}([9ab]);)'; 
                       $pattern .= '|'; 
                       $pattern .= '|(&#0{0,8}([9|10|13]);)'; 
                       $pattern .= ')*'; 
                   } 
                   $pattern .= $ra[$i][$j]; 
               } 
               $pattern .= '/i'; 
               $replacement = substr($ra[$i], 0, 2).'<x>'.substr($ra[$i], 2); // add in <> to nerf the tag 
               $val = preg_replace($pattern, $replacement, $val); // filter out the hex tags 
               if ($val_before == $val) { 
                   // no replacements were made, so exit the loop 
                   $found = false; 
               } 
           } 
       } 
       return $val; 
    }
    ?>