php中preg
欢迎进入Linux社区论坛,与200万技术人员互动交流 >>进入 php中preg_match函数的使用方法: 语法: int preg_match ( string pattern, string subject [, array matches [, int flags]] ) 在 subject 字符串中搜索与 pattern 给出的正则表达式相匹配的内容. 如
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php中preg_match函数的使用方法:
语法:
int preg_match ( string pattern, string subject [, array matches [, int flags]] )
在 subject 字符串中搜索与 pattern 给出的正则表达式相匹配的内容.
如果提供了 matches,则其会被搜索的结果所填充.$matches[0] 将包含与整个模式匹配的文本,$matches[1] 将包含与第一个捕获的括号中的子模式所匹配的文本,以此类推.
flags 可以是下列标记:
PREG_OFFSET_CAPTURE
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,第二项为其偏移量.本标记自 PHP 4.3.0 起可用.
flags 参数自 PHP 4.3.0 起可用.
preg_match() 返回 pattern 所匹配的次数.要么是 0 次(没有匹配)或 1 次,因为 preg_match() 在第一次匹配之后将停止搜索.preg_match_all() 则相反,会一直搜索到 subject 的结尾处.如果出错 preg_match() 返回 FALSE.
提示: 如果只想查看一个字符串是否包含在另一个字符串中,不要用 preg_match().可以用 strpos() 或 strstr() 替代,要快得多.
例1. 在文本中搜索“php”
// 模式定界符后面的 “i” 表示不区分大小写字母的搜索
if (preg_match (“/php/i”, “PHP is the web scripting language of choice.”)) {
print “A match was found.”;
} else {
print “A match was not found.”;
}
?>
例2. 搜索单词“web”
/* 模式中的 \b 表示单词的边界,因此只有独立的 “web” 单词会被匹配,
* 而不会匹配例如 “webbing” 或 “cobweb” 中的一部分 */
if (preg_match (“/\bweb\b/i”, “PHP is the web scripting language of choice.”)) {
print “A match was found.”;
} else {
print “A match was not found.”;
}
if (preg_match (“/\bweb\b/i”, “PHP is the website scripting language of choice.”)) {
print “A match was found.”;
} else {
print “A match was not found.”;
}
?>
例3. 从 URL 中取出域名
// 从 URL 中取得主机名
preg_match(“/^(http:\/\/)?([^\/]+)/i”,
$host = $matches[2];
// 从主机名中取得后面两段
preg_match(“/[^\.\/]+\.[^\.\/]+$/”, $host, $matches);
echo “domain name is: {$matches[0]}\n”;
?>
输出:
domain name is: php.net
与之相似的函数还有preg_match_all,在此不作过多介绍.

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