regular expression (php function), regularexpression_PHP tutorial

regular expression (php function), regularexpression

1. Regular expression is a tool for string search and matching

2. Commonly used regular expression functions in php

• preg_match($pattern, $subject)
• preg_match_all($pattern, $subject, array &$matches)
• preg_replace($pattern, $replacement, $subject)
• preg_filter($pattern, $replacement, $subject)
• preg_grep($pattern, array $input)
• preg_split($pattern, $subject)
• preg_quote($str)

3. Function description

$pattern = regular expression

$subject = matching objective function

　(1) preg_match() and preg_match_all(): return the number of times the result was matched

• preg_match($pattern, $subject, [array &$matches]): only matches once, the result is 0 or 1, the third parameter is optional, and the third parameter represents the reference of the address
• preg_match($pattern, $subject, array &$matches): Match all, the result is 0,1,2...

eg:

　$pattern='/[0-9]/';

　$subject = 'weuyr3ui76as83s0ck9';

　$m1 = $m2 = array();

t1 = grep_match($pattern, $subject, $m1);

t2 = grep_match_all($pattern, $subject, $m2);

Result: m1 = array([0]=>3)

　m2 = array([0]=>array([0]=>3,[1]=>7,[2]=>6,[3]=>8,[4] =>3,[5]=>0,[6]=>9))

　t1 = 1

　t2 = 7

　(2) preg_replace and preg_filter: support array replacement

• preg_replace($pattern, $replacement, $subject): retain the values ​​that have been replaced and those that have not been replaced
• preg_filter($pattern, $replacement, $subject): retain the replaced value

eg one:

　$pattern='/[0-9]/';

　$subject = 'weuyr3ui76as83s0ck9';

　$replacement = 'ying';

　$str1 = preg_replace($pattern, $replacement, $subject);

　$str2 = preg_filter($pattern, $replacement, $subject);

Result:

$str1 = 'weuyryinguiyingyingasyingyingsyingckying'

$str2 = 'weuyryinguiyingyingasyingyingsyingckying'

eg two:

　$pattern = array('/[0123]/', '/[456]/', '/[789]/')

　$replacement = array('Ah', 'La', '妦')

Result:

$str1 = 'weuyrah ui 妦拉as妦ah sah ck 妦'

　$str2 = 'weuyrahui妦拉as妦ahsahck妦'

eg three:

$subject = array('weuy', 'r3ui', '76as83', 's', '0ck9');

Result:

　$str1 = array([0]=>weuy, [1]=>rui, [2]=>妦拉as妦Ah, [3]=>s, [4]= >Ah ck 妦)

　$str2 = array([1]=>rui, [2]=>妦拉as妦妦ah, [4]=>ahck妦)

　(3) grep_grep($pattern, array $input): A emasculated version of grep_filter(), only matching, no replacement

eg:

　$pattern='/[0-9]/';

$subject = array('weuy', 'r3ui', '76as83', 's', '0ck9');

　$arr = preg_grep($pattern, $subject);

Result:

　$arr = array([1]=>r3ui, [2]=>76as83, [4]=>0ck9)

　(4) grep_split($pattern, $subject): explode is a subset of this function

eg:

　$pattern = '/[0-9]/';

　$subject = 'You 2 are so good at 3!'

　$arr = preg_split($pattern, $subject);

Result:

　$arr = ([0]=>You, [1]=>Okay, [2]=>Ah!)