在對于字符串的替換上，我們已經學過了不少的方法。但在做練習題的時候，我們會對多個字符串進行替換。從方法的實用性來說，str_replace就非常適合處理多個字符串的替換問題。下面我們就php中str_replace的概念、語法、參數、返回值進行講解，然后帶來替換的實例分享。
?php
/**
* 安全過濾函數
*
* @param $string
* @return string
*/
function safe_replace($string) {
$string = str_replace('%20','',$string);
$string = str_replace('%27','',$string);
$string = str_replace('%2527','',$string);
$string = str_replace('*','',$string);
$string = str_replace('"','quot;',$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;
}
?>
?php
/**
* 返回經addslashes處理過的字符串或數組
* @param $string 需要處理的字符串或數組
* @return mixed
*/
function new_addslashes($string) {
if(!is_array($string)) return addslashes($string);
foreach($string as $key => $val) $string[$key] = new_addslashes($val);
return $string;
}
?>
?php
//對請求的字符串進行安全處理
/*
$safestep
0 為不處理，
1 為禁止不安全HTML內容(javascript等)，
2 完全禁止HTML內容，并替換部份不安全字符串（如：eval(、union、CONCAT(、--、等）
*/
function StringSafe($str, $safestep=-1){
$safestep = ($safestep > -1) ? $safestep : 1;
if($safestep == 1){
$str = preg_replace("#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;
}
}
?>
?php
/**
+----------------------------------------------------------
* 輸出安全的html，用于過濾危險代碼
+----------------------------------------------------------
* @access public
+----------------------------------------------------------
* @param string $text 要處理的字符串
* @param mixed $tags 允許的標簽列表，如 table|td|th|td
+----------------------------------------------------------
* @return string
+----------------------------------------------------------
*/
static public function safeHtml($text, $tags = null)
{
$text = trim($text);
//完全過濾注釋
$text = preg_replace('/!--?.*-->/','',$text);
//完全過濾動態代碼
$text = preg_replace('/?|?'.'>/','',$text);
//完全過濾js
$text = preg_replace('/script?.*/script>/','',$text);
$text = str_replace('[','#091;',$text);
$text = str_replace(']','#093;',$text);
$text = str_replace('|','#124;',$text);
//過濾換行符
$text = preg_replace('/ ? /','',$text);
//br
$text = preg_replace('/br(s/)?'.'>/i','[br]',$text);
$text = preg_replace('/([br]s*){10,}/i','[br]',$text);
//過濾危險的屬性，如：過濾on事件lang js
while(preg_match('/([^>]+)(lang|on|action|background|codebase|dynsrc|lowsrc)[^>]+/i',$text,$mat)){
$text=str_replace($mat[0],$mat[1],$text);
}
while(preg_match('/([^>]+)(window.|javascript:|js:|about:|file:|document.|vbs:|cookie)([^>]*)/i',$text,$mat)){
$text=str_replace($mat[0],$mat[1].$mat[3],$text);
}
if( empty($allowTags) ) { $allowTags = self::$htmlTags['allow']; }
//允許的HTML標簽
$text = preg_replace('/('.$allowTags.')( [^>[]]*)>/i','[12]',$text);
//過濾多余html
if ( empty($banTag) ) { $banTag = self::$htmlTags['ban']; }
$text = preg_replace('//?('.$banTag.')[^>]*>/i','',$text);
//過濾合法的html標簽
while(preg_match('/([a-z]+)[^>[]]*>[^>]*/1>/i',$text,$mat)){
$text=str_replace($mat[0],str_replace('>',']',str_replace('','[',$mat[0])),$text);
}
//轉換引號
while(preg_match('/([[^[]]*=s*)("|')([^2=[]]+)2([^[]]*])/i',$text,$mat)){
$text=str_replace($mat[0],$mat[1].'|'.$mat[3].'|'.$mat[4],$text);
}
//空屬性轉換
$text = str_replace('''','||',$text);
$text = str_replace('""','||',$text);
//過濾錯誤的單個引號
while(preg_match('/[[^[]]*("|')[^[]]*]/i',$text,$mat)){
$text=str_replace($mat[0],str_replace($mat[1],'',$mat[0]),$text);
}
//轉換其它所有不合法的 >
$text = str_replace('','lt;',$text);
$text = str_replace('>','gt;',$text);
$text = str_replace('"','quot;',$text);
//反轉換
$text = str_replace('[','',$text);
$text = str_replace(']','>',$text);
$text = str_replace('|','"',$text);
//過濾多余空格
$text = str_replace(' ',' ',$text);
return $text;
}
?>
?php
function RemoveXSS($val) {
// remove all non-printable characters. CR(0a) and LF(0b) and TAB(9) are allowed
// this prevents some character re-spacing such as javascript>
// note that you have to handle splits with , , and later since they *are* allowed in some // inputs
$val = preg_replace('/([x00-x08,x0b-x0c,x0e-x19])/', '', $val);
// straight replacements, the user should never need these since they're normal characters
// this prevents like IMG SRC=@avascript:alert('XSS')>
$search = 'abcdefghijklmnopqrstuvwxyz';
$search .= 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
$search .= '1234567890!@#$%^*()';
$search .= '~`";:?+/={}[]-_|'';
for ($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;
}
?>
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