How to extract only Chinese characters from php string

Two methods: 1. Use preg_match_all() with regular filter strings, the syntax "preg_match_all("/[\x{4e00}-\x{9fff}] /u","$str", $arr);"; 2. Use preg_replace() with regular expressions to search for non-Chinese letters in the string and replace them with empty characters. The syntax is "preg_replace("/[^\x{4E00}-\x{9FFF} ] /u",'',$str)".

The operating environment of this tutorial: windows7 system, PHP version 8.1, DELL G3 computer

In php, you can use the following two functions To extract only the Chinese characters of the string

• preg_replace() function

• preg_match_all() function

Method 1: Use the preg_match_all() function

preg_match_all() function with the regular expression "/[\x{4e00}-\x {9fff}] /u" can filter the string and only get Chinese characters.

will store the matching Chinese characters into an array one by one (the array is specified by the third parameter).

<?php
header("Content-type:text/html;charset=utf-8");
$str = "欢迎4546来到php这里。zblog,我的?#$%^天呀&())*(&^";
echo $str;
preg_match_all("/[\x{4e00}-\x{9fff}]+/u","$str",$arr);
var_dump($arr);
?>

The result value can then be spliced ​​into a string using the join() function.

join('',$arr[0])

Instructions:

1) preg_match_all() function

preg_match_all() function will search for strings All results in

preg_match_all(pattern,subject,matches,flags,offset)

are described as follows:

• pattern: The pattern to be searched, which is the defined regular expression;
• subject: the string to be searched;
• matches: optional parameter (multidimensional array), used to store all matching results, the array sorting is specified by $flags;
• flags: optional Select parameters, which can be used in combination with the following tags (note that PREG_PATTERN_ORDER and PREG_SET_ORDER cannot be used at the same time):
  • PREG_PATTERN_ORDER: The results are sorted into $matches[0] to save all matches of the complete pattern, $matches[1] to save the first All matches in a subgroup, and so on.
  • PREG_SET_ORDER: The results are sorted as $matches[0] contains all matches (including subgroups) from the first match, $matches[1] contains all matches (including subgroups) from the second match ), and so on.
  • PREG_OFFSET_CAPTURE: If this flag is passed, each found match is returned with its offset relative to the target string increased. Note that this will change each match string element in $matches to be one where the 0th element is the match string and the 1st element is the offset of the match string within the subject.
• offset: Optional parameter, $offset is used to start searching from the specified position in the target string (unit is byte).

The preg_match_all() function can return the number of matches for pattern (possibly 0), or FALSE if an error occurs.

2) join() function

join() function returns a string composed of array elements.

join() function is an alias of implode() function.

join(separator,array)

• separator: Optional. Specifies what is placed between array elements. Default is "" (empty string).

• array: required. Arrays to be combined into strings.

Return value: Returns a string composed of array elements.

Method 2: Use the preg_replace() function

preg_match_all() function with the regular expression "/[^\x{ 4E00}-\x{9FFF}] /u” Search for non-Chinese letters in the string and replace them with empty characters ''.

<?php
header("Content-type:text/html;charset=utf-8");
$str= &#39;php中文网!-=1548&#39;;
echo $str."<br>";
$pattern = "/[^\x{4E00}-\x{9FFF}]+/u";
$newstr=preg_replace($pattern,&#39;&#39;, $str);preg_match_all("/[\x{4e00}-\x{9fff}]+/u","$str",$arr);
var_dump($newstr);
?>

Description: preg_replace()

preg_replace() function can perform search and replacement of regular expressions and is a powerful String replacement processing function, the syntax format of this function is as follows:

preg_replace($pattern, $replacement, $subject [, $limit = -1 [, &$count]])

The parameter description is as follows:

• $pattern: The pattern to be searched, which can be a string or an array of strings;
• $replacement: The string or array of strings used for replacement. If this argument is a string and $pattern is an array, then all patterns are replaced with this string. If $pattern and $replacement are both arrays, each $pattern is replaced with the corresponding element in $replacement. If there are fewer elements in $replacement than in $pattern, the extra $pattern is replaced with the empty string.
• $subject: The string or string array to be searched and replaced. If $subject is an array, the search and replacement will be performed on each element of $subject, and the return value will also be one array.
• $limit: Optional parameter, the maximum number of substitutions per pattern on each $subject. Default is -1 (infinite).
• $count: Optional parameter, if specified, will be filled with the number of completed substitutions.

If $subject is an array, the preg_replace() function will return an array, otherwise it will return a string.

If the function preg_replace() finds a match, it will return the replaced $subject, otherwise it will return the unchanged $subject. Each parameter of the preg_replace() function (except the parameter $limit) can be an array. If the $pattern parameter and the $replacement parameter are both arrays, the function will process the keys in the order they appear in the array. If an error occurs, NULL is returned.

The parameter $replacement can contain back references \\n or $n, the latter is preferred syntactically. Each such reference will be replaced by the text captured by the nth capturing subgroup that was matched. n can be 0-99, with \\0 and $0 representing the complete pattern matching text.

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