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php中preg正则函数使用

2015-05-27

1.preg_match和preg_match_all的区别
preg_match和 preg_match_all区别是preg_match只匹配一次。而preg_match_all全部匹配，直到字符串结束。例：

 string 'abcde' (length=5)array (size=1)  0 =>    array (size=3)      0 => string 'abcde' (length=5)      1 => string 'abcde' (length=5)      2 => string 'abcde' (length=5) */?>

2.贪婪模式和非贪婪模式的区别
如：String str="abcaxc";
　　Patter p="ab*c";
贪婪匹配:正则表达式一般趋向于最大长度匹配，也就是所谓的贪婪匹配。如上面使用模式p匹配字符串str，结果就是匹配到：abcaxc(ab*c)。
非贪婪匹配：就是匹配到结果就好，较少的匹配字符。如上面使用模式p匹配字符串str，结果就是匹配到：abc(ab*c)。
例：

 string 'http://www.baidu/.com?url=www.sina.com' (length=38)  1 => string '//www.baidu/.com?url=www.sina.' (length=30)array (size=2)  0 => string 'http://www.baidu/.com' (length=21)  1 => string '//www.baidu/.' (length=13) */?>

3.preg_match_all参数PREG_PATTERN_ORDER(默认)和PREG_SET_ORDER的区别

]+>(.*)[^>]+>|U",    "start: this is a testend",    $out1);var_dump($out1);echo('PREG_SET_ORDER');preg_match_all("|]+>(.*)[^>]+>|U",    "start: this is a testend",    $out2, PREG_SET_ORDER);var_dump($out2);/*PREG_PATTERN_ORDERarray (size=2)  0 =>    array (size=3)      0 => string 'start: ' (length=14)      1 => string 'this is a test' (length=21)      2 => string 'end' (length=10)  1 =>    array (size=3)      0 => string 'start: ' (length=7)      1 => string 'this is a test' (length=14)      2 => string 'end' (length=3)PREG_SET_ORDERarray (size=3)  0 =>    array (size=2)      0 => string 'start: ' (length=14)      1 => string 'start: ' (length=7)  1 =>    array (size=2)      0 => string 'this is a test' (length=21)      1 => string 'this is a test' (length=14)  2 =>    array (size=2)      0 => string 'end' (length=10)      1 => string 'end' (length=3) */?>