1、function nl2br($str)
功能：Inserts HTML line breaks before all newlines in a string
示例：<?php echo nl2br("foo isn't\n bar"); ?>
结果：\n会被HTML的换行替换

2、array preg_split ( string pattern, string subject [, int limit [, int flags]])
返回一个数组，包含 subject 中沿着与 pattern 匹配的边界所分割的子串。
如果指定了 limit，则最多返回 limit 个子串，如果 limit 是 -1，则意味着没有限制，可以用来继续指定可选参数 flags。
flags 可以是下列标记的任意组合（用按位或运算符 | 组合）：
PREG_SPLIT_NO_EMPTY
如果设定了本标记，则 preg_split() 只返回非空的成分。
PREG_SPLIT_DELIM_CAPTURE
如果设定了本标记，定界符模式中的括号表达式也会被捕获并返回。本标记添加于 PHP 4.0.5。
PREG_SPLIT_OFFSET_CAPTURE
如果设定了本标记，如果设定本标记，对每个出现的匹配结果也同时返回其附属的字符串偏移量。注意这改变了返回的数组的值，使其中的每个单元也是一个数组，其中第一项为匹配字符串，第二项为其在 subject 中的偏移量。本标记自 PHP 4.3.0 起可用。

3、int ord ( string string)
Returns the ASCII value of the first character of string. This function complements chr().

4、ob_start()(PHP 4 )
ob_start -- Turn on output buffering

5、ob_get_clean()(PHP 4 >= 4.3.0)
ob_get_clean -- Get current buffer contents and delete current output buffer

6、array array_merge ( array array1, array array2 [, array ...])
array_merge() 将两个或多个数组的单元合并起来，一个数组中的值附加在前一个数组的后面。返回作为结果的数组。
如果输入的数组中有相同的字符串键名，则该键名后面的值将覆盖前一个值。然而，如果数组包含数字键名，后面的值将不会覆盖原来的值，而是附加到后面。

7、array get_html_translation_table ( int table [, int quote_style])
get_html_translation_table() will return the translation table that is used internally for htmlspecialchars() and htmlentities().
There are two new constants (HTML_ENTITIES, HTML_SPECIALCHARS) that allow you to specify the table you want. And as in the htmlspecialchars() and htmlentities() functions you can optionally specify the quote_style you are working with. The default is ENT_COMPAT mode. See the description of these modes in htmlspecialchars().
Translation Table Example
<?php
$trans = get_html_translation_table(HTML_ENTITIES);
$str = "Hallo & & Kr漤er";
$encoded = strtr($str, $trans);
?>
The $encoded variable will now contain: "Hallo & <Frau> & Krämer".

8、string strtr ( string str, string from, string to)
string strtr ( string str, array replace_pairs)
This function returns a copy of str, translating all occurrences of each character in from to the corresponding character in to and returning the result.
If from and to are different lengths, the extra characters in the longer of the two are ignored.

9、mixed preg_replace ( mixed pattern, mixed replacement, mixed subject [, int limit])
在 subject 中搜索 pattern 模式的匹配项并替换为 replacement。如果指定了 limit，则仅替换 limit 个匹配，如果省略 limit 或者其值为 -1，则所有的匹配项都会被替换。
replacement 可以包含 \\n 形式或（自 PHP 4.0.4 起）$n 形式的逆向引用，首选使用后者。每个此种引用将被替换为与第 n 个被捕获的括号内的子模式所匹配的文本。n 可以从 0 到 99，其中 \\0 或 $0 指的是被整个模式所匹配的文本。对左圆括号从左到右计数（从 1 开始）以取得子模式的数目。
对替换模式在一个逆向引用后面紧接着一个数字时（即：紧接在一个匹配的模式后面的数字），不能使用熟悉的 \\1 符号来表示逆向引用。举例说 \\11，将会使 preg_replace() 搞不清楚是想要一个 \\1 的逆向引用后面跟着一个数字 1 还是一个 \\11 的逆向引用。本例中的解决方法是使用 \${1}1。这会形成一个隔离的 $1 逆向引用，而使另一个 1 只是单纯的文字。

10、mysql_real_escape_string(PHP 4 >= 4.3.0)
mysql_real_escape_string -- 转义 SQL 语句中使用的字符串中的特殊字符，并考虑到连接的当前字符集

11、string htmlspecialchars ( string string [, int quote_style [, string charset]])
Certain characters have special significance in HTML, and should be represented by HTML entities if they are to preserve their meanings. This function returns a string with some of these conversions made; the translations made are those most useful for everyday web programming. If you require all HTML character entities to be translated, use htmlentities() instead.
This function is useful in preventing user-supplied text from containing HTML markup, such as in a message board or guest book application. The optional second argument, quote_style, tells the function what to do with single and double quote characters. The default mode, ENT_COMPAT, is the backwards compatible mode which only translates the double-quote character and leaves the single-quote untranslated. If ENT_QUOTES is set, both single and double quotes are translated and if ENT_NOQUOTES is set neither single nor double quotes are translated.
The translations performed are:
'&' (ampersand) becomes '&'
'"' (double quote) becomes '"' when ENT_NOQUOTES is not set.
''' (single quote) becomes ''' only when ENT_QUOTES is set.
'<' (less than) becomes '<'
'>' (greater than) becomes '>'

12、string strip_tags ( string str [, string allowable_tags])
This function tries to return a string with all HTML and PHP tags stripped from a given str. It uses the same tag stripping state machine as the fgetss() function.
You can use the optional second parameter to specify tags which should not be stripped.

13、string htmlentities ( string string [, int quote_style [, string charset]])
This function is identical to htmlspecialchars() in all ways, except with htmlentities(), all characters which have HTML character entity equivalents are translated into these entities.

14、string stripslashes ( string str)
Returns a string with backslashes stripped off. (\' becomes ' and so on.) Double backslashes (\\) are made into a single backslash (\).
An example use of stripslashes() is when the PHP directive magic_quotes_gpc is on (it's on by default), and you aren't inserting this data into a place (such as a database) that requires escaping. For example, if you're simply outputting data straight from an HTML form.

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