1、修饰符

2、元字符

3、函数

/*

* 搜索字符串

* 搜索数组中的所有元素，返回由与某个模式匹配的所有元素组成的数组

* array preg_grep(string psttern,array input[,flag])

*/

$foods = array ("pasta", "steak", "fish", "potatoes" );

var_dump ( preg_grep ( "/^p/", $foods ) );

/*

* 搜索模式

* 在字符串中搜索模式，如果存在返回TRUE否则返回FALSE

* boolean preg_match(string pattern,string string[,array matches[,int flags[,int offset]]])

*/

$line = "Vim is the greatest word processor ever created!";

if (preg_match ( "/\bVim\b/i", $line, $match )) {

    var_dump ( $match );

}

/*

* 匹配模式的所有出现

* 在字符串中匹配模式的所有出现，以便通过可选的输入参数order所指定的顺序

* int preg_match_all(string pattern,string string,array pattern-array[,int order])

*/

$userinfo = "Name:<b>Zeev Suraski</b><br>Title:<b>PHP Curu</b>";

preg_match_all ( "/<b>(.*)<\/b>/U", $userinfo, $pat_array );

var_dump ( $pat_array );

/*

* 界定特殊的正则表达式字符

* 在每个对于正则表达式语法而言有特殊含义的字符前插入一个反斜线。这些特殊字符包括$^*()+={}|\\:[]<>

* string preg_quote(string str[,string delimitrer])

*/

$text = "Tickets for the bout are going for $500.";

echo preg_quote ( $text );

/*

* 替换模式的所有出现

* mixed preg_replace(mixed pattern,mixed replacement,mixed str[,int limit])

*/

$text = "This is a link to http://www.wk.com/.";

echo preg_replace ( "/http:\/\/(.*)\//", "<a href=\"\${0}\">\${0}</a>", $text );

/*

* 创建定制的替换函数

* mixed preg_replace_callback(mixed pattern,callback callback,mixed str[,int limit])

*/

function acronym($matches) {

    $acronyms = array(

        'WWW' => 'World Wide Web',

        'IRS' => 'Internal Revenue Service',

        'PDF' => 'Portable Document Format'

    );

    if(isset($acronyms[$matches[1]]))

        return $matches[1] . "(" .$acronyms[$matches[1]] . ")";

    else

        return $matches[1];

}

$text = "The <acronym>ISR</acronym> offsers tax form in <acronym>PDF</acronym> format on the <acronym>WWW</acronym>.";

$newtext=preg_replace_callback("/<acronym>(.*)<\/acronym>/U", 'acronym', $text);

var_dump($newtext);

/*

* 以不区分大小写的方式将字符串划分为不同的元素

* array preg_split(string pattern,string string[,int limit[,int flags]])

*/

$delimitedText = "Jason++Gilmore+++++++Columbus+++OH";

$fields = preg_split ( "/\+{1,}/", $delimitedText );

var_dump ( $fields );