ereg_replace — 正则表达式替换
ereg — 正则表达式匹配
eregi_replace — 不区分大小写的正则表达式替换
eregi — 不区分大小写的正则表达式匹配
split — 用正则表达式将字符串分割到数组中
spliti — 用正则表达式不区分大小写将字符串分割到数组中
sql_regcase — 产生用于不区分大小的匹配的正则表达式
使用示例：
<?php // returns true if "abc" is found anywhere in $string. ereg("abc", $string); // returns true if "abc" is found at the beginning of $string. ereg("^abc", $string); // returns true if "abc" is found at the end of $string. ereg("abc$", $string); // returns true if client browser is netscape 2, 3 or msie 3. eregi("(ozilla.[23]|msie.3)", $_server["http_user_agent"]); // places three space separated words into $regs[1], $regs[2] and $regs[3]. ereg("([[:alnum:]]+) ([[:alnum:]]+) ([[:alnum:]]+)", $string, $regs); // put a <br /> tag at the beginning of $string. $string = ereg_replace("^", "<br />", $string); // put a <br /> tag at the end of $string. $string = ereg_replace("$", "<br />", $string); // get rid of any newline characters in $string. $string = ereg_replace("\n", "", $string); ?>