Home >Backend Development >PHP Tutorial >PHP regular expression introductory tutorial [translated], regular expression introductory tutorial_PHP tutorial
PHP regular expression introductory tutorial [translated], regular expression introductory tutorial_PHP tutorial
- WBOYOriginal
- 2016-07-12 08:52:21966browse
PHP regular expression introductory tutorial [translated], regular expression introductory tutorial
Mind map Click on the image below to see the specific content!
$regex = '/^http://([w.] )/([w] )/([w] ).html$/i';
$str = 'http://www.youku.com/show_page/id_ABCDEFG.html';
$matches = array();
if(preg_match($regex, $str, $matches)){
var_dump($matches);
}
echo "n";
|
$matches[0] in preg_match will contain the string matching the entire pattern.
The code using the "#" delimiter is as follows. At this time, "/" will not be escaped!
$regex = '#^http://([w.] )/([w] )/([w] ).html$#i';
$str = 'http://www.youku.com/show_page/id_ABCDEFG.html';
$matches = array();
if(preg_match($regex, $str, $matches)){
var_dump($matches);
}
echo "n";
|
¤ Modifier: used to change the behavior of regular expressions.
The last one we see in ('/^http://([w.] )/([w] )/([w] ).html/i') i" is the modifier, which means ignoring case, and another one we often use is "x" which means ignoring spaces.
Contribute code:
$regex = '/HELLO/';
$str = 'hello word';
$matches = array();
if(preg_match($regex, $str, $matches)){
echo 'No i:Valid Successful!',"n";
}
if(preg_match($regex.'i', $str, $matches)){
echo 'YES i:Valid Successful!',"n";
}
|
¤ Character field: [w] The part expanded with square brackets is the character field.
¤ Qualifier: such as [w]{3,5} or [w]* or [w]. The symbols after [w] all represent qualifiers. The specific meaning is now introduced.
{3,5} means 3 to 5 characters. {3,} is more than 3 characters, {,5} is up to 5 characters, and {3} is three characters.
* represents 0 to multiple
means 1 to more.
¤ caret
^:
& gt; placed in the character domain (such as: [^w]) indicate the negative (excluding meaning) - "reverse selection"
can be placed before the expression to start with the current character. (/^n/i, means starting with n).
Note, we often call "" "escape character". Used to escape some special symbols, such as ".", "/"
Wildcards (lookarounds): Assert the presence or absence of certain characters in certain strings! There are two types of lookarounds: lookaheads (forward lookup ?=) and lookbehinds (reverse lookup?<=). > Format: Positive lookup: (?=) corresponding to (?!) means negative meaning Reverse pre-lookup: (?<=) The corresponding (?
$regex = '/(?<=c)d(?=e)/'; /* d 前面紧跟c, d 后面紧跟e*/
$str = 'abcdefgk';
$matches = array();
if(preg_match($regex, $str, $matches)){
var_dump($matches);
}
echo "n";
Negative meaning:
$regex = '/(?<!c)d(?!e)/'; /* d 前面不紧跟c, d 后面不紧跟e*/
$str = 'abcdefgk';
$matches = array();
if(preg_match($regex, $str, $matches)){
var_dump($matches);
}
echo "n";
|
>Character width: zero Verify zero character codes
$regex = '/HE(?=L)LO/i';
$str = 'HELLO';
$matches = array();
if(preg_match($regex, $str, $matches)){
var_dump($matches);
}
echo "n";
|
Cannot print the result!
$regex = '/HE(?=L)LLO/i';
$str = 'HELLO';
$matches = array();
if(preg_match($regex, $str, $matches)){
var_dump($matches);
}
echo "n";
|
Can print out the results!
Explanation: (?=L) means HE is followed by an L character. However, (?=L) itself does not occupy a character and must be distinguished from (L), which itself occupies one character.
capture data Groupings without specifying a type will be retrieved for later use. > indicates that the type refers to the wildcard character. Therefore, only those without question marks at the beginning of the parentheses can be captured. > References within the same expression are called backreferences. > Calling format: number (such as 1).
$regex = '/^(Chuanshanjia)[ws!] 1$/';
$str = 'Chuanshanjia thank Chuanshanjia';
$matches = array();
if(preg_match($regex, $str, $matches)){
var_dump($matches);
}
echo "n";
|
> Avoid capturing data Format:(?:pattern) Advantages: It will keep the number of effective back references to a minimum and the code will be clearer. >Named capturing group Format: (?P
$regex = '/(?P<author>chuanshanjia)[s]Is[s](?P=author)/i';
$str = 'author:chuanshanjia Is chuanshanjia';
$matches = array();
if(preg_match($regex, $str, $matches)){
var_dump($matches);
}
echo "n";
|
Run results
Lazy matching (remember: two operations will be performed, please see the principle part below)
Format: Qualifier?
Principle: "?": If there is a qualifier in front of it, the smallest data will be used. For example, "*" will take 0, and " " will take 1. If it is {3,5}, 3 will be taken.
Look at the following two codes first:
Code 1.
<?php
$regex = '/heL*/i';
$str = 'heLLLLLLLLLLLLLLLL';
if(preg_match($regex, $str, $matches)){
var_dump($matches);
}
echo "n";
|
Result 1.
Code 2
<?php
$regex = '/heL*?/i';
$str = 'heLLLLLLLLLLLLLLLL';
if(preg_match($regex, $str, $matches)){
var_dump($matches);
}
echo "n";
|
Result 2
Code 3, use " "
<?php
$regex = '/heL ?/i';
$str = 'heLLLLLLLLLLLLLLLL';
if(preg_match($regex, $str, $matches)){
var_dump($matches);
}
echo "n";
|
Result 3
Code 4, use {3,5}
<?php
$regex = '/heL{3,10}?/i';
$str = 'heLLLLLLLLLLLLLLLL';
if(preg_match($regex, $str, $matches)){
var_dump($matches);
}
echo "n";
|
Result 4
$regex = '/
^host=(?<!.)([d.] )(?!.) (?#主机地址)
|
([w!@#$%^&*()_ -] ) (?#用户名)
|
([w!@#$%^&*()_ -] ) (?#密码)
(?!|)$/ix';
$str = 'host=192.168.10.221|root|123456';
$matches = array();
if(preg_match($regex, $str, $matches)){
var_dump($matches);
}
echo "n";
|
special characters
| 特殊字符 | 解释 |
| * | 0到多次 |
| 1到多次还可以写成{1,} | |
| ? | 0或1次 |
| . | 匹配除换行符外的所有单个的字符 |
| w | [a-zA-Z0-9_] |
| s | 空白字符(空格，换行符，回车符）[tnr] |
| d | [0-9] |