[Muxi_k] - PHP regular expression Getting Started

Regular Expressions

php regular expression study notes

What is a regular expression

1. Regular expressions (Regular Expressions (Perl-Compatible)), is a matching pattern

2. Regular expression itself is a string

3. Regular expressions to be used in the corresponding function

• There are two sets of regular expression libraries, both functionally similar in PHP, only a slight difference in efficiency

  • A use provided by the PCRE library preg_prefixed function named
  • Provided by a POSIX extended, used to ereg_function prefixed

note

• PCRE Perl language derived from sign
• PCRE syntax supports more features with powerful than POSIX

---

Regular grammar

<?php
$reg = "/a\d/i"

• Delimiters, you can use a variety of commonly used for the//
• Atom: smallest matching unit \a\(to be placed delimiter)
• Metacharacters: can not be used alone, modification atoms, is used to extend the capabilities and limitations atoms /\d/(to be placed delimiter)
• Correction coding mode: correction, a mode (regular correction) /a/i(to be placed outside the delimiter)

---

Regular expression atoms

Atom is the smallest unit of a regular expression, an expression of at least one atom

All those atoms are not specified by the character element is displayed as a non-printing characters and printable characters, particularly into five categories. (All characters are atomic)

1. Ordinary characters as atoms: a-z A-Z 0-9other
2. After the transfer element and some special characters as character atoms:
   • All of the punctuation, but the statement is of special significance as a symbol needs to be escaped before atoms, such as \"\'\*\+\?\., etc.
3. Some non-printing characters as atoms: such as\f\n\r\t\cx
4. Use "universal character type" atoms as: As:\d\D\w\W\s\S
5. Since atoms table definition ([]) as the atoms: such as:'/[apj]sp/' '/[^apj]sp/'

General character as the atom

• Printable charactersa-z A-Z 0-9 !@#$%^&*()...
• Non-printing characters\n...

$str = "this is a ^ test ";

$reg = "/\^/";

if (preg_match($reg, $str, $arr)) {
    echo "正则表达式{$reg}和{$str}匹配成功!\n";
    print_r($arr);
} else {
    echo "匹配失败";
}

正则表达式/\^/和this is a ^ test 匹配成功!
Array
(
    [0] => ^
)

'\': Escape sign:

After some special characters and characters as atom transfer element

• Meaningful symbols may be transformed into meaningless atoms, e.g./\^/
• It may be meaningless characters turn into meaningful atoms, for example /\t/(tab key)
• a-z A-Z 0-9 All of these characters does not make sense, with no sense of escape is there can be added from time to increase the

In addition to a-z A-Z 0-9these symbols do not need to transfer the best escape when other symbols, most of the special symbols have special meaning

---

The use of "universal character type"

\d	On behalf of any of a number
\D	A representative of any non-numeric

# /\d/
$str = "this is a 123 test 11";
// 匹配所有数字
$reg = "/\d/";
------------------------------------------
正则表达式/\d/和this is a 123 test 11匹配成功!
Array
(
    [0] => Array
        (
            [0] => 1
            [1] => 2
            ...
        )

)

# /\D/
$str = "this is a 123 test 11";

// 匹配所有数字
$reg = "/\D/";
------------------------------------------
正则表达式/\D/和this is a 123 test 11匹配成功!
Array
(
    [0] => Array
        (
            [0] => t
            [3] => s
            [4] =>
            [5] => i
            ...
        )

)

---

\w	It represents any word az AZ 0-9 _
\W	It stands for any word except for a non-az AZ 0-9 _ all characters

# /\w/
$str = "!@$@%%^%$@____";
// 匹配所有字
$reg = "/\w/";

------------------------------------
正则表达式/\w/和!@$@%%^%$@____匹配成功!
Array
(
    [0] => Array
        (
            [0] => _
            [1] => _
            ...
        )
)

# \/W\
正则表达式/\W/和!@$@%%^%$@____匹配成功!
Array
(
    [0] => Array
        (
            [0] => !
            [1] => @
            [2] => $
            [3] => @
            ...
        )

)

---

\s	Representatives blank
\S	A representative of any non-blank

# /\s/
$str = "qw
we   rt";
----------
Array
(
    [0] => Array
        (
            [0] =>
            [1] =>
            [2] =>
            [3] =>
        )

)

#/\S/
正则表达式/\S/和qw
we   rt匹配成功!
Array
(
    [0] => Array
        (
            [0] => q
            [1] => w
            [2] => w
            [3] => e
            [4] => r
            [5] => t
        )

---

Custom Table atom

Use []to specify

# [469]
正则表达式/[469]/和1243456768909匹配成功!
Array
(
    [0] => Array
        (
            [0] => 4
            [1] => 4
            [2] => 6
            [3] => 6
            [4] => 9
            [5] => 9
        )

)

Range can be specified by ' -' represents

正则表达式/[1-5]/和1243456768909匹配成功!
Array
(
    [0] => Array
        (
            [0] => 1
            [1] => 2
            [2] => 4
            [3] => 3
            [4] => 4
            [5] => 5
        )

)

non-^

All non-matching numbers

正则表达式/[^1-4]/和ass2423匹配成功!
Array
(
    [0] => Array
        (
            [0] => a
            [1] => s
            [2] => s
        )
)

.point

Behalf of all

---

Note

Regular expressions are commonly used in non-printing characters

Atomic characters	Meaning Description
\cx	Match control characters specified by the x, such as \ cM matches a Control-M or a carriage return, or one of x must az AZ
\f	Match for a website page, equivalent to \ x0x or \ cL
\n	Matches a newline, equivalent to \ X0A or \ cJ
\r	Matching a carriage return, equivalent to \ x0d or \ cM
\t	Matching a tab, equivalent to \ x09 or \ the cI
\v	Matching a vertical tab, equivalent to \ X0B or \ The cK
…	…

Regular expression metacharacters

Expression alone can not be used in the positive, for modification atoms

• ' *' In front of the atoms used to modify one or more of 0 may occur

# /go*gle/
正则表达式/go*gle/和this gggggoogle is a test 匹配成功!
Array
(
    [0] => Array
        (
            [0] => google
        )
)

• ' +' Matches or multiple front views of 1 atom (at least once in front of atoms)

正则表达式/g+oogle/和this gggggoogle is a test 匹配成功!
Array
(
    [0] => Array
        (
            [0] => gggggoogle
        )
)

• ' ?' Matches one or more times before its atoms (atoms not occur several times in front)

#正则表达式/go?gle/和this gogle is a test 匹配成功!
Array
(
    [0] => Array
        (
            [0] => gogle
        )

• {n} Indicate that the previous atom occurs exactly n times

# 正则表达式/go{2}gle/和this google is a test 匹配成功!
Array
(
    [0] => Array
        (
            [0] => google
        )
)

• {n,} Indicate that the previous occurrence atoms is not less than n

# 正则表达式/go{2,}gle/和this google is a test 匹配成功!
Array
(
    [0] => Array
        (
            [0] => google
        )
)

• {n,m} It indicates that the previous atom appears at least n times, the most frequent m

# 正则表达式/go{1,3}gle/和this google is a test 匹配成功!
Array
(
    [0] => Array
        (
            [0] => google
        )
)

• ()
  • Change priority
  • The change larger than the small atomic atom
  • Sub-mode, the entire expression is a large model, parentheses are independent of each sub-model
  • Backreferences

正则表达式/orac(le|my)/和this oracmysql is a test 匹配成功!
Array
(
    [0] => Array
        (
            [0] => oracmy
        )

    [1] => Array
        (
            [0] => my
        )
)

正则表达式/orac(mysql)*/和this oracmysql is a mysql 匹配成功!
Array
(
    [0] => Array
        (
            [0] => oracmysql
        )

    [1] => Array
        (
            [0] => mysql
        )

)

正则表达式/(http|ftp):\/\/\www(.*)?\.(com|net)/和this http://www.baidu.com oracmysql ftp://www.exp.net is a mysql 匹配成功!
Array
(
    [0] => Array
        (
            [0] => http://www.baidu.com oracmysql ftp://www.exp.net
        )

    [1] => Array
        (
            [0] => http
        )

    [2] => Array
        (
            [0] => .baidu.com oracmysql ftp://www.exp
        )

    [3] => Array
        (
            [0] => net
        )

)

正则表达式/\d{4}(-|\/)\d{2}\1\d{2}/和this 2020-03-06 2020/03/06 匹配成功!
Array
(
    [0] => Array
        (
            [0] => 2020-03-06
            [1] => 2020/03/06
        )

    [1] => Array
        (
            [0] => -
            [1] => /
        )

)

Metacharacters table

Metacharacters	Meaning Description
*	Match zero, one or more times before their atoms
+	Match front atoms or more 1
?	Match front atom of 0 or 1
!	Branch selection matches two or more
{n}	Indicate that the previous atom occurs exactly n times
{n,}	Indicate that the previous occurrence atoms is not less than n times
{n,m}	It indicates that the previous atom appears at least n times m times the most frequent
^或、A	Matches the start position of the input string (or multi-mode at the beginning of the downlink, either immediately after a newline)
\$或\Z	(Or after the beginning of the downlink multi-mode, both followed by a line feed) end of the matched input character string
\b	Matching word boundaries
\B	In addition to the matching part of a word boundary
()	Matching a whole atom, i.e. mode unit, to be understood that a plurality of single atoms by atoms of large

Mode correction code (single character)

1. Correction coding mode write delimiter outside (right)

Example:

"/go*gle/i"

2. Mode correction code, a character that is a function

3. effect:

   • Mode correction code can correct explanation regular expressions, the expansion of the regular expressions

• i: Fixed case-insensitive regular expressions (the default is case-sensitive)

正则表达式/test/i和this is a Test匹配成功!
Array
(
    [0] => Array
        (
            [0] => Test
        )
)

• m The multi-line regarded as multi-line (the default being put multiple lines regarded as one line)

正则表达式/^is/m和this
is a Test匹配成功!
Array
(
    [0] => Array
        (
            [0] => is
        )
)

• sCorrection regular expression can match a newline (by default. Can not match newline)

正则表达式/Te.*st/s和this is a Te
st匹配成功!
Array
(
    [0] => Array
        (
            [0] => Te
st
        )
)

• sCorrection regular expressions, you can omit the blank

正则表达式/web server/ix和this is a WebServer匹配成功!
Array
(
    [0] => Array
        (
            [0] => WebServer
        )

)

• U(*, +) Regular expression comparison greedy greedy U can cancel mode (not often used for general use (. *?))

Write regular expressions

1. Regular expression is a language, to learn to open your mind
2. Column demand

Write regular match url

<?php

$str = "
    这是http://www.example.com网站
    这是http://www.xxx.net/index.php网站
    这是http://www.example.cn/php网站
    这是http://www.demo.org/login.php?user=aaa网站
    这是https://www.test.top网站
    这是https://news.baidu.top网站
    这是ftp://news.baidu.top网站
";


$reg = "/(https?|ftps?):\/\/(.*?).(.*?).(com|net|org|cn|top)([\w\.\/\=\?\&]*)?/";

preg_match_all($reg, $str, $arr);
print_r($arr);

Write regular match email

<?php

$str = "
    这是[email protected]邮箱
    这是[email protected]邮箱
    这是[email protected]邮箱
    这是[email protected]邮箱
";


$reg = "/\w+([-+]\w+)*@\w+(-.\w+)*\.\w+/i";

preg_match_all($reg, $str, $arr);
print_r($arr);

Use regular expressions

Segmentation, matching, search, replace

1. String handling functions (fast processing, but some do)
2. Regular Expression Functions (powerful, but less efficient)

Note: The string handling functions can be handled, would not have a regular process

Find a match:

• strstr()
• strpos ()
• substr()

Regular match

• preg_match ()
• preg_match_all()
• preg_grep ()

String split

• explode()
• implode()
• join()

Regular division

• preg_split ()

String replacement

• str_replace()

Regular replacement

• preg_replace()