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php中str_replace替换实例讲解

程序员文章站 2022-03-16 07:57:14
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在对于字符串的替换上,我们已经学过了不少的方法。但在做练习题的时候,我们会对多个字符串进行替换。从方法的实用性来说,str_replace就非常适合处理多个字符串的替换问题。下面我们就php中str_replace的概念、语法、参数、返回值进行讲解,然后带来替换的实例分享。

1、概念
str_replace() 函数以其他字符替换字符串中的一些字符(区分大小写)。

该函数区分大小写。请使用 str_ireplace() 函数执行不区分大小写的搜索。

2、语法
str_replace(find,replace,string,count)
3、参数
Find、replace、string、count

4、返回值
返回带有替换值的字符串或数组。

5、实例
创建一个PHP示例文件;然后通过“tr_replace($vowels, “”,”Hello World of PHP”);”方法替换多个字符串即可。
echo str_replace(array(“m”,”i”),array(“n”,”z”),”my name is jim!”)

  1. echo str_replace(array('m','i'),'n',"my name is jim!");
  2. $vowels = array("a", "e", "i", "o", "u", "A", "E", "I", "O", "U");
  3. $onlyconsonants = str_replace($vowels, "","Hello World of PHP");
  4. echo $onlyconsonants;

知识点扩展:

PHP利用str_replace防注入的方法
<?php
/**

  1. * 安全过滤函数
  2. *
  3. * @param $string
  4. * @return string
  5. */
  6. function safe_replace($string) {
  7. $string = str_replace('%20','',$string);
  8. $string = str_replace('%27','',$string);
  9. $string = str_replace('%2527','',$string);
  10. $string = str_replace('*','',$string);
  11. $string = str_replace('"','&quot;',$string);
  12. $string = str_replace("'",'',$string);
  13. $string = str_replace('"','',$string);
  14. $string = str_replace(';','',$string);
  15. $string = str_replace('<','&lt;',$string);
  16. $string = str_replace('>','&gt;',$string);
  17. $string = str_replace("{",'',$string);
  18. $string = str_replace('}','',$string);
  19. $string = str_replace('','',$string);
  20. return $string;
  21. }
  22. ?>
  23. <?php
  24. /**
  25. * 返回经addslashes处理过的字符串或数组
  26. * @param $string 需要处理的字符串或数组
  27. * @return mixed
  28. */
  29. function new_addslashes($string) {
  30. if(!is_array($string)) return addslashes($string);
  31. foreach($string as $key => $val) $string[$key] = new_addslashes($val);
  32. return $string;
  33. }
  34. ?>
  35. <?php
  36. //对请求的字符串进行安全处理
  37. /*
  38. $safestep
  39. 0 为不处理,
  40. 1 为禁止不安全HTML内容(javascript等),
  41. 2 完全禁止HTML内容,并替换部份不安全字符串(如:eval(、union、CONCAT(、--、等)
  42. */
  43. function StringSafe($str, $safestep=-1){
  44. $safestep = ($safestep > -1) ? $safestep : 1;
  45. if($safestep == 1){
  46. $str = preg_replace("#script:#i", "script:", $str);
  47. $str = preg_replace("#<[/]{0,1}(link|meta|ifr|fra|scr)[^>]*>#isU", '', $str);
  48. $str = preg_replace("#[ ]{1,}#", ' ', $str);
  49. return $str;
  50. }else if($safestep == 2){
  51. $str = addslashes(htmlspecialchars(stripslashes($str)));
  52. $str = preg_replace("#eval#i", 'eval', $str);
  53. $str = preg_replace("#union#i", 'union', $str);
  54. $str = preg_replace("#concat#i", 'concat', $str);
  55. $str = preg_replace("#--#", '--', $str);
  56. $str = preg_replace("#[ ]{1,}#", ' ', $str);
  57. return $str;
  58. }else{
  59. return $str;
  60. }
  61. }
  62. ?>
  63. <?php
  64. /**
  65. +----------------------------------------------------------
  66. * 输出安全的html,用于过滤危险代码
  67. +----------------------------------------------------------
  68. * @access public
  69. +----------------------------------------------------------
  70. * @param string $text 要处理的字符串
  71. * @param mixed $tags 允许的标签列表,如 table|td|th|td
  72. +----------------------------------------------------------
  73. * @return string
  74. +----------------------------------------------------------
  75. */
  76. static public function safeHtml($text, $tags = null)
  77. {
  78. $text = trim($text);
  79. //完全过滤注释
  80. $text = preg_replace('/<!--?.*-->/','',$text);
  81. //完全过滤动态代码
  82. $text = preg_replace('/<?|?'.'>/','',$text);
  83. //完全过滤js
  84. $text = preg_replace('/<script?.*/script>/','',$text);
  85. $text = str_replace('[','[',$text);
  86. $text = str_replace(']',']',$text);
  87. $text = str_replace('|','|',$text);
  88. //过滤换行符
  89. $text = preg_replace('/ ? /','',$text);
  90. //br
  91. $text = preg_replace('/<br(s/)?'.'>/i','[br]',$text);
  92. $text = preg_replace('/([br]s*){10,}/i','[br]',$text);
  93. //过滤危险的属性,如:过滤on事件lang js
  94. while(preg_match('/(<[^><]+)(lang|on|action|background|codebase|dynsrc|lowsrc)[^><]+/i',$text,$mat)){
  95. $text=str_replace($mat[0],$mat[1],$text);
  96. }
  97. while(preg_match('/(<[^><]+)(window.|javascript:|js:|about:|file:|document.|vbs:|cookie)([^><]*)/i',$text,$mat)){
  98. $text=str_replace($mat[0],$mat[1].$mat[3],$text);
  99. }
  100. if( empty($allowTags) ) { $allowTags = self::$htmlTags['allow']; }
  101. //允许的HTML标签
  102. $text = preg_replace('/<('.$allowTags.')( [^><[]]*)>/i','[12]',$text);
  103. //过滤多余html
  104. if ( empty($banTag) ) { $banTag = self::$htmlTags['ban']; }
  105. $text = preg_replace('/</?('.$banTag.')[^><]*>/i','',$text);
  106. //过滤合法的html标签
  107. while(preg_match('/<([a-z]+)[^><[]]*>[^><]*</1>/i',$text,$mat)){
  108. $text=str_replace($mat[0],str_replace('>',']',str_replace('<','[',$mat[0])),$text);
  109. }
  110. //转换引号
  111. while(preg_match('/([[^[]]*=s*)("|')([^2=[]]+)2([^[]]*])/i',$text,$mat)){
  112. $text=str_replace($mat[0],$mat[1].'|'.$mat[3].'|'.$mat[4],$text);
  113. }
  114. //空属性转换
  115. $text = str_replace('''','||',$text);
  116. $text = str_replace('""','||',$text);
  117. //过滤错误的单个引号
  118. while(preg_match('/[[^[]]*("|')[^[]]*]/i',$text,$mat)){
  119. $text=str_replace($mat[0],str_replace($mat[1],'',$mat[0]),$text);
  120. }
  121. //转换其它所有不合法的 < >
  122. $text = str_replace('<','&lt;',$text);
  123. $text = str_replace('>','&gt;',$text);
  124. $text = str_replace('"','&quot;',$text);
  125. //反转换
  126. $text = str_replace('[','<',$text);
  127. $text = str_replace(']','>',$text);
  128. $text = str_replace('|','"',$text);
  129. //过滤多余空格
  130. $text = str_replace(' ',' ',$text);
  131. return $text;
  132. }
  133. ?>
  134. <?php
  135. function RemoveXSS($val) {
  136. // remove all non-printable characters. CR(0a) and LF(0b) and TAB(9) are allowed
  137. // this prevents some character re-spacing such as <javascript>
  138. // note that you have to handle splits with , , and later since they *are* allowed in some // inputs
  139. $val = preg_replace('/([x00-x08,x0b-x0c,x0e-x19])/', '', $val);
  140. // straight replacements, the user should never need these since they're normal characters
  141. // this prevents like <IMG SRC=@avascript:alert('XSS')>
  142. $search = 'abcdefghijklmnopqrstuvwxyz';
  143. $search .= 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
  144. $search .= '1234567890!@#$%^&*()';
  145. $search .= '~`";:?+/={}[]-_|'';
  146. for ($i = 0; $i < strlen($search); $i++) {
  147. // ;? matches the ;, which is optional
  148. // 0{0,7} matches any padded zeros, which are optional and go up to 8 chars
  149. // @ @ search for the hex values
  150. $val = preg_replace('/(&#[xX]0{0,8}'.dechex(ord($search[$i])).';?)/i', $search[$i], $val);//with a ;
  151. // @ @ 0{0,7} matches '0' zero to seven times
  152. $val = preg_replace('/(&#0{0,8}'.ord($search[$i]).';?)/', $search[$i], $val); // with a ;
  153. }
  154. // now the only remaining whitespace attacks are , , and
  155. $ra1 = Array('javascript', 'vbscript', 'expression', 'applet', 'meta', 'xml', 'blink', 'link', 'style', 'script', 'embed', 'object', 'iframe', 'frame', 'frameset', 'ilayer', 'layer', 'bgsound', 'title', 'base');
  156. $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');
  157. $ra = array_merge($ra1, $ra2);
  158. $found = true; // keep replacing as long as the previous round replaced something
  159. while ($found == true) {
  160. $val_before = $val;
  161. for ($i = 0; $i < sizeof($ra); $i++) {
  162. $pattern = '/';
  163. for ($j = 0; $j < strlen($ra[$i]); $j++) {
  164. if ($j > 0) {
  165. $pattern .= '(';
  166. $pattern .= '(&#[xX]0{0,8}([9ab]);)';
  167. $pattern .= '|';
  168. $pattern .= '|(&#0{0,8}([9|10|13]);)';
  169. $pattern .= ')*';
  170. }
  171. $pattern .= $ra[$i][$j];
  172. }
  173. $pattern .= '/i';
  174. $replacement = substr($ra[$i], 0, 2).'<x>'.substr($ra[$i], 2); // add in <> to nerf the tag
  175. $val = preg_replace($pattern, $replacement, $val); // filter out the hex tags
  176. if ($val_before == $val) {
  177. // no replacements were made, so exit the loop
  178. $found = false;
  179. }
  180. }
  181. }
  182. return $val;
  183. }
  184. ?>