在對於字串的替換上，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串的替換問題。下面我們就php中str_replace的概念、語法、引數、返回值進行講解，然後帶來替換的例項分享。

1、概念

str_replace() 函式以其他字元替換字串中的一些字元（區分大小寫）。

該函式區分大小寫。請使用 str_ireplace() 函式執行不區分大小寫的搜尋。

2、語法

str_replace(find,replace,string,count)

3、引數

Find、replace、string、count

4、返回值

返回帶有替換值的字串或陣列。

5、例項

建立一個PHP示例檔案；然後通過“tr_replace($vowels,"","Hello World of PHP");”方法替換多個字串即可。

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;

知識點擴充套件：

PHP利用str_replace防注入的方法

 <?php
 /**
 * 安全過濾函式
 *
 * @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);
 $string = str_replace('<','&lt;',$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處理過的字串或陣列
 * @param $string 需要處理的字串或陣列
 * @return mixed
 */
 function new_addslashes($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
 /*
 $safestep
 0 為不處理，
 1 為禁止不安全HTML內容(javascript等)，
 2 完全禁止HTML內容，並替換部份不安全字串（如：eval(、union、CONCAT(、--、等）
 */
 function StringSafe($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);
 return $str;
 }else{
 return $str;
 }
 }
 ?>

 <?php
 /**
 +----------------------------------------------------------
 * 輸出安全的html，用於過濾危險程式碼
 +----------------------------------------------------------
 * @access public
 +----------------------------------------------------------
 * @param string $text 要處理的字串
 * @param mixed $tags 允許的標籤列表，如 table|td|th|td
 +----------------------------------------------------------
 * @return string
 +----------------------------------------------------------
 */
 static public function safeHtml($text,$tags = null)
 {
 $text = trim($text);
 //完全過濾註釋
 $text = preg_replace('/<!--?.*-->/',$text);
 //完全過濾動態程式碼
 $text = preg_replace('/<?|?'.'>/',$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);
 $text = preg_replace('/([br]s*){10,}/i',$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',$mat[1].$mat[3],$text);
 }
 if( empty($allowTags) ) { $allowTags = self::$htmlTags['allow']; }
 //允許的HTML標籤
 $text = preg_replace('/<('.$allowTags.')( [^><[]]*)>/i','[12]',$text);
 //過濾多餘html
 if ( empty($banTag) ) { $banTag = self::$htmlTags['ban']; }
 $text = preg_replace('/</?('.$banTag.')[^><]*>/i',$text);
 //過濾合法的html標籤
 while(preg_match('/<([a-z]+)[^><[]]*>[^><]*</1>/i',str_replace('>',']',str_replace('<','[',$mat[0])),$text);
 }
 //轉換引號
 while(preg_match('/([[^[]]*=s*)("|')([^2=[]]+)2([^[]]*])/i',$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',str_replace($mat[1],$mat[0]),$text);
 }
 //轉換其它所有不合法的 < >
 $text = str_replace('<',$text);
 $text = str_replace('>',$text);
 $text = str_replace('"',$text);
 //反轉換
 $text = str_replace('[','<','>','"',$text);
 //過濾多餘空格
 $text = str_replace(' ',$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[$i]).';?)/',$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[$i],2).'<x>'.substr($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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