Regular expressions for PHP learning

What we now mean by regular expressions is basically perl-compliant regular expressions. Posix-style regular expressions are largely unused, so they have not been recommended since PHP5.3, and the next version of PHP will probably remove them.

On regular expressions, I want to focus on a book on regular expressions because they are too complex, so I'll just cover some functions that are compatible with perl-style regular expressions.

1. The delimiter
Delimiters represent the beginning and end of a regular expression, usually expressed as slashes (/). In PHP (which is not yet tested in other languages), it can also be replaced with other non-alphanumeric characters. Such as /\d+/ and #\d+# represent the same regular expression \d+. You can also use pairs of braces, brackets, and braces as delimiters, such as [\d+].

2. The function
Match function: preg_match(); And preg_match_all ();
Preg_replace ();
Split function: preg_split();
Filter function: preg_grep();

Sample code:

 
$a = <<< TEXT 
aaaaaaa 15 
bbbbbbb 16 
TEXT; 
$ret = preg_match(/(w+) (d+)/, $a, $match); 
// $ret : 1 
// $match : array(aaaaaaa 15 ' , aaaaaaa, 15 ' ) 

$ret = preg_match_all(/(w+) (d+)/, $a, $match); 
// $ret : 2 
// $match : array( 
// array(aaaaaaa 15 ' , bbbbbbb 16 ' ), 
// array(bbbbbbb, bbbbbbb), 
// array(15 ' , 16 ' ), 
// ) 

$ret = preg_match_all(/(w+) (d+)/, $a, $match, PREG_SET_ORDER); 
// $ret : 2 
// $match : array( 
// array(aaaaaaa 15 ' , bbbbbbb, 15 ' ), 
// array(bbbbbbb 16 ' , bbbbbbb, 16 ' ), 
// ) 

$b = preg_replace(/(w+) (d+)/, 1, 2 ' , $a); 
// $b : aaaaaaa, 15 
// bbbbbbb, 16 '  

$c = preg_split(/s/, $a); 
// $c : array(aaaaaaa, 15 ' , bbbbbbb, 16 ' ) 

$files = array(aa.txt, bb.xls, cc.txt); 
$txtFiles = preg_grep(/.*.txt/, $files); 
// $txtFiles : array(aa.txt, cc.txt) 

Reference:
PHP programming, 2003, chapter 4 strings, regular expressions