How to exclude a certain string in php regular expression

How to use php regular expression not to contain a certain string: first create a PHP sample file; then use the regular expression "preg_match("/[^(abc)]/s", $str, $arr); "Just implement the judgment that it does not contain a certain string.

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Common functions strstr($str, "abc" );
Regular matching preg_match(”/(abc)?/is”, $str);
But if you want to match a string that does not contain a certain string, it is more troublesome to use regular matching
If The problem can be solved without using the regular expression !strstr($str, “abc”);
But with the regular expression, there is only this, “/^((?!abc).)*$/is”

//------------------------------------------------ 
代码如下:
 <?php 
  $str = "dfadfadf765577abc55fd"; 
  $pattern_url = "/^((?!abc).)*$/is"; 
  if (preg_match($pattern_url, $str)){ 
  echo "不含有abc！"; 
  }else{ 
  echo "含有abc！"; 
  } 
  ?> 
 
 //------------------------------------------------ 
 结果为：false，含有abc！ 
 $str = “2b3c4d5c”; 
 注意：[^(abc)] 这个语法是逐个检查$str中的字符是否不在 a b c中， 
 preg_match(”/[^(abc)]/s”, $str, $arr); 
 其中字符 2 就不在 a b c 中，所以$arr返回值为2; 
 同时匹配，包含字符串 “abc”，而且不包含字符串 “xyz” 
 “/(abc)[^((?!xyz).)*$]/s”

The following is a supplement:

There are many methods to determine whether a string contains another string, as follows:

1. Common Function

strstr($str, "abc");

2. Regular matching

preg_match("/(abc)/is", $str);

But if you want to match a string that does not contain a certain string, it is more troublesome to use regular matching.
1. If you don’t use regular expressions, you can solve the problem as follows

!strstr($str, "abc");

2. But with regular expressions, that’s all.

preg_match("/^((?!abc).)*$/is", $str);

Complete code example

The code is as follows:

$str = "dfadfadf765577abc55fd"; 
 $pattern_url = "/^((?!abc).)*$/is"; 
 if (preg_match($pattern_url, $str)) 
 { 
 echo "不含有abc！"; 
 } 
 else 
 { 
 echo "含有abc！"; 
 }

The result is: false, containing abc!

Match at the same time, the regular expression that contains the string "abc" and does not contain the string "xyz":

preg_match("/(abc)[^((?!xyz) .)*$]/is", $str);

This method is effective. I use it as follows:

 (?:(?!<\/p>).|\n)*? //匹配不含</p>的一个字符串

But in the end, it was found that this method is extremely inefficient. You can consider using it when processing very short text (there are a dozen words, or at most dozens of words, that need to match the same part of the regular expression), but you should not use it when parsing a large article or when you need to change the matching time in multiple places. , consider using other methods instead (such as: first parse out the text to match the regular expression, and then verify whether a certain text exists in it), regular expressions are not very effective for matching text fields that do not contain specific strings. method.

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