Regular expression (php function), regularexpression

Regular expression (php function), regularexpression

1. Regular Expressions are a string search and matching tool.

2. Common 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 = matched Target Function

(1) preg_match () and preg_match_all (): number of times that return matches the result

• Preg_match ($ pattern, $ subject, [array & $ matches]): match only once. The result is 0 or 1. The third parameter is not required. The third parameter indicates the address reference.
• Preg_match ($ pattern, $ subject, array & $ matches): returns 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: array replacement is supported.

• Preg_replace ($ pattern, $ replacement, $ subject): retains the values that are replaced or not 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 = 'weuyr Ying ui Ying as Ying s Ying ck Ying'

$ Str2 = 'weuyr Ying ui Ying as Ying s Ying ck Ying'

Eg two:

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

$ Replacement = array ('Ah', 'La', 'day ')

Result:

$ Str1 = 'weuyr, ui, as, s, ck'

$ Str2 = 'weuyr, ui, as, s, ck'

Eg three:

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

Result:

$ Str1 = array ([0] => weuy, [1] => r, ui, [2] => as, [3] => s, [4] => Ah ck)

$ Str2 = array ([1] => r, ui, [2] => as, [4] => Ah ck)

(3) grep_grep ($ pattern, array $ input): castrated grep_filter (). Only matching is performed without 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 the function.

Eg:

$ Pattern = '/[0-9]/';

$ Subject = 'Hello! 3! '

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

Result:

$ Arr = ([0] => you, [1] => good, [2] => ah !)