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。

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

知识点扩展：

PHP利用str_replace防注入的方法

1. <?php
2. /**
3. * 安全过滤函数
4. *
5. * @param $string
6. * @return string
7. */
8. function safe_replace($string) {
9. $string = str_replace('%20','',$string);
10. $string = str_replace('%27','',$string);
11. $string = str_replace('%2527','',$string);
12. $string = str_replace('*','',$string);
13. $string = str_replace('"','&quot;',$string);
14. $string = str_replace("'",'',$string);
15. $string = str_replace('"','',$string);
16. $string = str_replace(';','',$string);
17. $string = str_replace('<','&lt;',$string);
18. $string = str_replace('>','&gt;',$string);
19. $string = str_replace("{",'',$string);
20. $string = str_replace('}','',$string);
21. $string = str_replace('','',$string);
22. return $string;
23. }
24. ?>
25. <?php
26. /**
27. * 返回经addslashes处理过的字符串或数组
28. * @param $string 需要处理的字符串或数组
29. * @return mixed
30. */
31. function new_addslashes($string) {
32. if(!is_array($string)) return addslashes($string);
33. foreach($string as $key => $val) $string[$key] = new_addslashes($val);
34. return $string;
35. }
36. ?>
37. <?php
38. //对请求的字符串进行安全处理
39. /*
40. $safestep
41. 0 为不处理，
42. 1 为禁止不安全HTML内容(javascript等)，
43. 2 完全禁止HTML内容，并替换部份不安全字符串（如：eval(、union、CONCAT(、--、等）
44. */
45. function StringSafe($str, $safestep=-1){
46. $safestep = ($safestep > -1) ? $safestep : 1;
47. if($safestep == 1){
48. $str = preg_replace("#script:#i", "ｓｃｒｉｐｔ：", $str);
49. $str = preg_replace("#<[/]{0,1}(link|meta|ifr|fra|scr)[^>]*>#isU", '', $str);
50. $str = preg_replace("#[ ]{1,}#", ' ', $str);
51. return $str;
52. }else if($safestep == 2){
53. $str = addslashes(htmlspecialchars(stripslashes($str)));
54. $str = preg_replace("#eval#i", 'ｅｖａｌ', $str);
55. $str = preg_replace("#union#i", 'ｕｎｉｏｎ', $str);
56. $str = preg_replace("#concat#i", 'ｃｏｎｃａｔ', $str);
57. $str = preg_replace("#--#", '－－', $str);
58. $str = preg_replace("#[ ]{1,}#", ' ', $str);
59. return $str;
60. }else{
61. return $str;
62. }
63. }
64. ?>
65. <?php
66. /**
67. +----------------------------------------------------------
68. * 输出安全的html，用于过滤危险代码
69. +----------------------------------------------------------
70. * @access public
71. +----------------------------------------------------------
72. * @param string $text 要处理的字符串
73. * @param mixed $tags 允许的标签列表，如 table|td|th|td
74. +----------------------------------------------------------
75. * @return string
76. +----------------------------------------------------------
77. */
78. static public function safeHtml($text, $tags = null)
79. {
80. $text = trim($text);
81. //完全过滤注释
82. $text = preg_replace('/<!--?.*-->/','',$text);
83. //完全过滤动态代码
84. $text = preg_replace('/<?|?'.'>/','',$text);
85. //完全过滤js
86. $text = preg_replace('/<script?.*/script>/','',$text);
87. $text = str_replace('[','&#091;',$text);
88. $text = str_replace(']','&#093;',$text);
89. $text = str_replace('|','&#124;',$text);
90. //过滤换行符
91. $text = preg_replace('/ ? /','',$text);
92. //br
93. $text = preg_replace('/<br(s/)?'.'>/i','[br]',$text);
94. $text = preg_replace('/([br]s*){10,}/i','[br]',$text);
95. //过滤危险的属性，如：过滤on事件lang js
96. while(preg_match('/(<[^><]+)(lang|on|action|background|codebase|dynsrc|lowsrc)[^><]+/i',$text,$mat)){
97. $text=str_replace($mat[0],$mat[1],$text);
98. }
99. while(preg_match('/(<[^><]+)(window.|javascript：|js:|about:|file:|document.|vbs:|cookie)([^><]*)/i',$text,$mat)){
100. $text=str_replace($mat[0],$mat[1].$mat[3],$text);
101. }
102. if( emptyempty($allowTags) ) { $allowTags = self::$htmlTags['allow']; }
103. //允许的HTML标签
104. $text = preg_replace('/<('.$allowTags.')( [^><[]]*)>/i','[12]',$text);
105. //过滤多余html
106. if ( emptyempty($banTag) ) { $banTag = self::$htmlTags['ban']; }
107. $text = preg_replace('/</?('.$banTag.')[^><]*>/i','',$text);
108. //过滤合法的html标签
109. while(preg_match('/<([a-z]+)[^><[]]*>[^><]*</1>/i',$text,$mat)){
110. $text=str_replace($mat[0],str_replace('>',']',str_replace('<','[',$mat[0])),$text);
111. }
112. //转换引号
113. while(preg_match('/([[^[]]*=s*)("|')([^2=[]]+)2([^[]]*])/i',$text,$mat)){
114. $text=str_replace($mat[0],$mat[1].'|'.$mat[3].'|'.$mat[4],$text);
115. }
116. //空属性转换
117. $text = str_replace('''','||',$text);
118. $text = str_replace('""','||',$text);
119. //过滤错误的单个引号
120. while(preg_match('/[[^[]]*("|')[^[]]*]/i',$text,$mat)){
121. $text=str_replace($mat[0],str_replace($mat[1],'',$mat[0]),$text);
122. }
123. //转换其它所有不合法的 < >
124. $text = str_replace('<','&lt;',$text);
125. $text = str_replace('>','&gt;',$text);
126. $text = str_replace('"','&quot;',$text);
127. //反转换
128. $text = str_replace('[','<',$text);
129. $text = str_replace(']','>',$text);
130. $text = str_replace('|','"',$text);
131. //过滤多余空格
132. $text = str_replace(' ',' ',$text);
133. return $text;
134. }
135. ?>
136. <?php
137. function RemoveXSS($val) {
138. // remove all non-printable characters. CR(0a) and LF(0b) and TAB(9) are allowed
139. // this prevents some character re-spacing such as <javascript>
140. // note that you have to handle splits with , , and later since they *are* allowed in some // inputs
141. $val = preg_replace('/([x00-x08,x0b-x0c,x0e-x19])/', '', $val);
142. // straight replacements, the user should never need these since they're normal characters
143. // this prevents like <IMG SRC=@avascript:alert('XSS')>
144. $search = 'abcdefghijklmnopqrstuvwxyz';
145. $search .= 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
146. $search .= '1234567890!@#$%^&*()';
147. $search .= '~`";:?+/={}[]-_|'';
148. for ($i = 0; $i < strlen($search); $i++) {
149. // ;? matches the ;, which is optional
150. // 0{0,7} matches any padded zeros, which are optional and go up to 8 chars
151. // @ @ search for the hex values
152. $val = preg_replace('/(&#[xX]0{0,8}'.dechex(ord($search[$i])).';?)/i', $search[$i], $val);//with a ;
153. // @ @ 0{0,7} matches '0' zero to seven times
154. $val = preg_replace('/(&#0{0,8}'.ord($search[$i]).';?)/', $search[$i], $val); // with a ;
155. }
156. // now the only remaining whitespace attacks are , , and
157. $ra1 = Array('javascript', 'vbscript', 'expression', 'applet', 'meta', 'xml', 'blink', 'link', 'style', 'script', 'embed', 'object', 'iframe', 'frame', 'frameset', 'ilayer', 'layer', 'bgsound', 'title', 'base');
158. $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');
159. $ra = array_merge($ra1, $ra2);
160. $found = true; // keep replacing as long as the previous round replaced something
161. while ($found == true) {
162. $val_before = $val;
163. for ($i = 0; $i < sizeof($ra); $i++) {
164. $pattern = '/';
165. for ($j = 0; $j < strlen($ra[$i]); $j++) {
166. if ($j > 0) {
167. $pattern .= '(';
168. $pattern .= '(&#[xX]0{0,8}([9ab]);)';
169. $pattern .= '|';
170. $pattern .= '|(&#0{0,8}([9|10|13]);)';
171. $pattern .= ')*';
172. }
173. $pattern .= $ra[$i][$j];
174. }
175. $pattern .= '/i';
176. $replacement = substr($ra[$i], 0, 2).'<x>'.substr($ra[$i], 2); // add in <> to nerf the tag
177. $val = preg_replace($pattern, $replacement, $val); // filter out the hex tags
178. if ($val_before == $val) {
179. // no replacements were made, so exit the loop
180. $found = false;
181. }
182. }
183. }
184. return $val;
185. }
186. ?>