unknown error PHP regular Unknown Modifier error solution

The following regular rules:

$a='2tóngdòng
垌3';
echo preg_replace('/[^<]*?/','',$a);

will prompt:

Warning: preg_replace(): Unknown modifier 'p' in E:phpLearntest.php on line 12

The reason is:

In the regular pattern, / is used as the delimiter, but the regular pattern also contains /, so this error will occur. PHP error The slash in the following is the ending delimiter.

Solution:

1. Add an escape character:

echo preg_replace('/[^<]*?/','',$a) ;

2. Change other delimiters: such as

echo preg_replace('{[^<]*?}','',$a) ;

The above introduces the unknown error PHP regular Unknown Modifier error solution, including the content of unknown error. I hope it will be helpful to friends who are interested in PHP tutorials.