Use of preg regular function in PHP

the difference between 1.preg_match and Preg_match_all
The difference between Preg_match and Preg_match_all is that preg_match matches only once. The Preg_match_all all match until the end of the string. Cases:

<?php//Note: Regular/a.+?e/is a non-greedy mode (because the quantifier ' + ' is appended with '? '), and if the use of/a.+?e/u is changed back to greedy mode Preg_match ("/a.+?e/", "ABCDEFGABCDEFGABCDEFG", $out 1);p reg_match_all ("/a.+?e/", "ABCDEFGABCDEFGABCDEFG", $out 2), Var_dump ($out 1); Var_dump ($out 2);/* Output: Array (size =1)  0 = 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. The difference between greedy and non-greedy modes
such as: String str= "ABCAXC";
Patter p= "Ab*c";
Greedy matching: Regular expressions tend to match the maximum length, which is called greedy matching. As above using pattern p to match string str, the result is matched to: Abcaxc (ab*c).
Non-greedy match: just match to the result is good, fewer matching characters. As above using pattern p to match string str, the result is matched to: ABC (AB*C).
Cases:

<?php$str = "http://www.baidu/.com?url=www.sina.com/";p reg_match ("/http: (. *) com/", $str, $matches 1); Greedy Match var_dump ($matches 1);p reg_match ("/http: (. *?)" com/", $str, $matches 2); Non-greedy match (quantifier ' * ' followed by '? ') Var_dump ($matches 2);/*array (size=2)  0 = 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 parameter Preg_pattern_order (default) and Preg_set_order differences

<?phpecho (' Preg_pattern_order ');p reg_match_all ("|<[^>]+> (. *) </[^>]+>| U "," <b>start: </b><b>this is a test</b><b>end</b> ", $out 1); Var_dump ($out 1); echo (' Preg_set_order ');p reg_match_all ("|<[^>]+> (. *) </[^>]+>| U "," <b>start: </b><b>this is a test</b><b>end</b> ", $out 2, preg_set_order); var_  Dump ($out 2);/*preg_pattern_orderarray (size=2) 0 = = Array (size=3) 0 = String ' <b>start: </b> ' (length=14) 1 = String ' <b>this is a test</b> ' (length=21) 2 = String ' &LT;B&GT;END&LT;/B&G t; ' (length=10) 1-= array (size=3) 0 = = String ' Start: ' (length=7) 1 = = String ' This is a test ' (Leng TH=14) 2 = String ' End ' (length=3) preg_set_orderarray (size=3) 0 = = Array (size=2) 0 = String ' &l T;b>start: </b> ' (length=14) 1 = String ' Start: ' (length=7) 1 = = Array (size=2) 0 = String ' <b>this is a test</b> ' (length=21) 1 = = String ' This is a test ' (length=14) 2 = = Array (size=2) 0 = String ' <b>end</b> ' (length=10) 1 = String ' End ' (length=3) */?>

Read MORE: Preg_match_all usage examples

Use of preg regular function in PHP