int preg_match ( string $pattern , string $subject [, array &$matches [, int $flags = 0 [, int $offset = 0 ]]] )

<?php
//从URL中获取主机名称
preg_match('@^(?:http://)?([^/]+)@i',
    "http://www.php.net/index.html", $matches);
$host = $matches[1];

//获取主机名称的后面两部分
preg_match('/[^.]+\.[^.]+$/', $host, $matches);

//domain name is: php.net
echo "domain name is: {$matches[0]}\n";
?>

<?php 
$pattern = '/www\.[^\.\/]+\.com/i';
$subject = 'www.baidu.com,www.qq.com,www.cnblogs.com';
preg_match($pattern,$subject,$matches);
/*
array (size=1)
  0 => string 'www.baidu.com' (length=13)
 */
var_dump($matches);
?>

int preg_match_all ( string $pattern , string $subject [, array &$matches [, int $flags = PREG_PATTERN_ORDER [, int $offset = 0 ]]] )

<?php 
$pattern = '/www\.[^\.\/]+\.com/i';
$subject = 'www.baidu.com,www.qq.com,www.cnblogs.com';
preg_match_all($pattern,$subject,$matches);
/*
array (size=1)
  0 => 
    array (size=3)
      0 => string 'www.baidu.com' (length=13)
      1 => string 'www.qq.com' (length=10)
      2 => string 'www.cnblogs.com' (length=15)
 */
var_dump($matches);
?>

array preg_grep ( string $pattern , array $input [, int $flags = 0 ] )

<?php 
$pattern = '/www\.[^\.\/]+\.com/i';
$subject = ['baidu.com','www.qq.com','www.cnblogs.com'];
var_dump (preg_grep($pattern,$subject));
/*
array (size=2)
  1 => string 'www.qq.com' (length=10)
  2 => string 'www.cnblogs.com' (length=15)
 */
?>

mixed preg_replace ( mixed $pattern , mixed $replacement , mixed $subject [, int $limit = -1 [, int &$count ]] )

<?php
$string = 'April 15, 2016';
$pattern = '/(\w+) (\d+), (\d+)/i';
$replacement = '${1}1,$3';

//April1,2016
echo preg_replace($pattern, $replacement, $string);
?>

<?php
$string = 'The quick brown fox jumped over the lazy dog.';
$patterns = array();
$patterns[0] = '/quick/';
$patterns[1] = '/brown/';
$patterns[2] = '/fox/';
$replacements = array();
$replacements[2] = 'bear';
$replacements[1] = 'black';
$replacements[0] = 'slow';

//The bear black slow jumped over the lazy dog.
echo preg_replace($patterns, $replacements, $string);
?>

mixed preg_replace_callback ( mixed $pattern , callable $callback , mixed $subject [, int $limit = -1 [, int &$count ]] )

<?php
// 将文本中的年份增加一年.
$text = "April fools day is 04/01/2002\n";
$text.= "Last christmas was 12/24/2001\n";
// 回调函数
function next_year($matches)
{
  // 通常: $matches[0]是完成的匹配
  // $matches[1]是第一个捕获子组的匹配
  // 以此类推
  return $matches[1].($matches[2]+1);
}
/*
April fools day is 04/01/2003
Last christmas was 12/24/2002
 */
echo preg_replace_callback(
            "|(\d{2}/\d{2}/)(\d{4})|",
            "next_year",
            $text);

?>

mixed preg_filter ( mixed $pattern , mixed $replacement , mixed $subject [, int $limit = -1 [, int &$count ]] )

<?php
$subject = array('1', 'a', '2', 'b', '3', 'A', 'B', '4'); 
$pattern = array('/\d/', '/[a-z]/', '/[1a]/'); 
$replace = array('A:$0', 'B:$0', 'C:$0'); 
/*
Array
(
    [0] => A:C:1
    [1] => B:C:a
    [2] => A:2
    [3] => B:b
    [4] => A:3
    [7] => A:4
)
 */
print_r(preg_filter($pattern, $replace, $subject)); 

/*
Array
(
    [0] => A:C:1
    [1] => B:C:a
    [2] => A:2
    [3] => B:b
    [4] => A:3
    [5] => A
    [6] => B
    [7] => A:4
)
 */
print_r(preg_replace($pattern, $replace, $subject)); 
?>

array preg_split ( string $pattern , string $subject [, int $limit = -1 [, int $flags = 0 ]] )

<?php
//使用逗号或空格(包含" ", \r, \t, \n, \f)分隔短语
$keywords = preg_split("/[\s,]+/", "hypertext language, programming");
/*
Array
(
    [0] => hypertext
    [1] => language
    [2] => programming
)
 */
print_r($keywords);
?>

string preg_quote ( string $str [, string $delimiter = NULL ] )

<?php
$keywords = '$40 for a g3/400';
$keywords = preg_quote($keywords, '/');
echo $keywords; // 返回 \$40 for a g3\/400
?>