Regular Expressions for PHP Learning_PHP Tutorial

What we all call regular expressions now basically refers to regular expressions that are compatible with Perl style. POSIX-style regular expressions are basically no longer used, so starting from PHP5.3, their use is no longer recommended. The related functions may be deleted in the next version of PHP.

Regarding regular expressions, because they are too complicated, I want to read a book on regular expressions in the future, so I will only introduce some functions that are compatible with Perl-style regular expressions.

1. Delimiter
delimiter indicates the beginning and end of the regular expression, usually represented by a slash (/). In PHP (not tested in other languages ​​yet), it can also be replaced by other non-alphanumeric characters. For example, /d+/ and #d+# represent the same regular expression d+. At the same time, you can also use pairs of parentheses, pairs of square brackets, and pairs of curly brackets as delimiters, such as [d+].

2. Functions
Matching function: preg_match(); and preg_match_all();
Replacement function: preg_replace();
Splitting function: preg_split() ;
Filter function: preg_grep();

Sample code:

Copy code The code is as follows:

$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

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