Preg_match--Perform regular expression matching. And only once, note the difference with the Preg_match_all.
Int
Preg_match(string pattern, string subject [, array matches [, int flags]]) in
SubjecT search in the string with
patternMatches the contents of the given regular expression. If you provide a
matches, it is populated with the results of the search. $matches [0] will contain text that matches the entire pattern,
$matches [1]Will contain the text that matches the child pattern in the first captured parenthesis, and so on.
Flagscan be the following tags:
preg_offset_captureIf this tag is set, the matching result for each occurrence also returns its subordinate string offset. Note that this changes the value of the returned array so that each cell is also an array, where the first item is the matching string, and the second item is its offset. This tag is available from PHP 4.3.0. The flags parameter is available from PHP 4.3.0. Preg_match () returns the number of times that pattern matches. Either 0 times (no match) or 1 times, because Preg_match () stops searching after the first match. If error Preg_match () returns FalsE If you just want to check if a string contains another string, do not use Preg_match (). Using Strpos () or STRSTR () overrides to complete the work is faster . [
The application of regular expressions in PHP
In PHP applications, regular expressions are mainly used to:
Regular match: matches the corresponding content according to the regular expression
Regular substitution: matches content according to regular expression and replaces
Regular segmentation: Splitting strings based on regular expressions
There are two types of regular expression functions in PHP, one is Perl-compatible regular expression functions, and the other is POSIX extended regular expression functions. There is little difference between the two, and it is recommended to use Perl-compatible regular expression functions, so the following are examples of Perl-compatible regular expression functions.
delimiter
The regular expression function of Perl compatibility mode, whose regular expression needs to be written in the delimiter. Any character that is not a letter, number, or backslash () can be used as a delimiter, usually we use/as a delimiter. For specific use, see the example below.
Tips
Although the regular expression function is very powerful, if you can do it with a normal string handler, try not to use regular expression functions, because regular expressions are much less efficient. About ordinary string processing functions.
Preg_match ()
The Preg_match () function is used to match a regular expression, successfully returning 1, otherwise returning 0.
Syntax:
int Preg_match (string pattern, string subject [, array matches])
parameter Description:
| Parameters |
Description |
| Pattern |
Regular expressions |
| Subject |
Objects that need to be matched for retrieval |
| Matches |
Optionally, an array of matching results is stored, $matches [0] will contain text that matches the entire pattern, $matches [1] will contain the text that matches the sub-pattern in the first captured parenthesis, and so on |
Example 1:
Copy CodeThe code is as follows:
<?php
if (Preg_match ("/php/i", "PHP is the Web scripting language of choice.", $matches)) {
Print "A match was found:". $matches [0];
} else {
Print "A match is not found.";
}
?>
Browser Output:
Copy CodeThe code is as follows:
A match was found:php
In this example, because I modifier is used, it is not case-sensitive to match PHP in the text.
Tips
Preg_match () The match is stopped after the first match succeeds, and if you want to match all results, that is, search to the end of subject, you need to use the Preg_match_all () function.
Example 2, get the host domain name from a URL:
Copy CodeThe code is as follows:
<?php
Get host name from URL
Preg_match ("/^" (HTTP//)? ( [^/]+)/I "," http://www.jb51.net/index.html ", $matches);
$host = $matches [2];
Get the next two paragraphs from the hostname
Preg_match ("/[^./]+.[ ^./]+$/", $host, $matches);
echo "domain name: {$matches [0]}";
?>
Browser Output:
Copy CodeThe code is as follows:
The domain name is: jb51.net
Preg_match_all ()
The Preg_match_all () function is used to perform a regular expression global match, which returns the number of times the entire pattern match succeeds (possibly 0), and returns FALSE if an error occurs.
Syntax:
int Preg_match_all (string pattern, string subject, array matches [, int flags])
parameter Description:
| Parameters |
Description |
| Pattern |
Regular expressions |
| Subject |
Objects that need to be matched for retrieval |
| Matches |
An array that stores the matching results |
| Flags |
Optionally, specify the order in which the matching results are placed in the matches, and the tags that are available for selection are:
- Preg_pattern_order: By default, the result is sorted so that $matches [0] is an array of all pattern matches, $matches [1] is an array of strings that match the sub-patterns in the first parenthesis, and so on
- Preg_set_order: Sorts the results so that $matches [0] is an array of the first set of matches, $matches [1] is an array of the second set of matches, and so on
- Preg_offset_capture: If you set this tag, the matching result for each occurrence also returns its subordinate string offset
|
The following example shows that the keywords (php) in all <pre></pre> tags in the text are shown in red.
Copy CodeThe code is as follows:
<?php
$str = "<pre> learning PHP is a happy thing. </pre><pre> all the phper need to work together! </pre> ";
$kw = "PHP";
Preg_match_all ('/<pre> ([ss]*?) </pre>/', $str, $mat);
for ($i =0; $i <count ($mat [0]); $i + +) {
$mat [0][$i] = $mat [1][$i];
$mat [0][$i] = str_replace ($kw, ' <span style= ' color: #ff0000 ">". $kw. ' </span> ', $mat [0][$i]);
$str = Str_replace ($mat [1][$i], $mat [0][$i], $str);
}
Echo $str;
?>
Regular matching Chinese characters
Regular matching Chinese characters are slightly different depending on the page encoding:
? gbk/gb2312 code: [x80-xff>]+ or [xa1-xff]+
? UTF-8 code: [x{4e00}-x{9fa5}]+/u
Example:
Copy CodeThe code is as follows:
<?php
$STR = "Learning php is a happy thing. ";
Preg_match_all ("/[x80-xff]+/", $str, $match);
UTF-8 using:
Preg_match_all ("/[x{4e00}-x{9fa5}]+/u", $str, $match);
Print_r ($match);
?>
output:
Copy CodeThe code is as follows:
Array
(
[0] = = Array
(
[0] = Learn
[1] = = is a happy thing.
)
)
Source: > .
Source: >
From for notes (Wiz)
int Preg_match (String pattern
