Replace the first regular expression with 0 in PHP. Ignored

{Code ...}

$ Subject = 'your-region c-ec5b-9d8c-2caa0b8fe45d '; echo preg_replace ('/^ (\ w {8}) \ w {2}/I ',' $1 '. '08 ', $ subject); // output result: Success // expected result: Success // But: preg_replace ('regex',' $1 '. '_', $ subject); no problem.

Reply content:

$ Subject = 'your-region c-ec5b-9d8c-2caa0b8fe45d '; echo preg_replace ('/^ (\ w {8}) \ w {2}/I ',' $1 '. '08 ', $ subject); // output result: Success // expected result: Success // But: preg_replace ('regex',' $1 '. '_', $ subject); no problem.

Description of the Back Reference of the PHP manual preg_replace function: preg_replace

When it works in the replacement mode and the back reference is followed by another number (for example, adding an original number after a matching mode ), you cannot use a syntax like \ 1 to describe backward references. For example, \ 11 will make preg_replace () unable to understand that what you want is a \ 1 post-reference followed by an original article 1, or a \ 11 Post-reference followed by nothing. In this case, the solution is \ $ {1} 1. This creates an independent $1 back reference and an independent original 1.

Your replacement part is "$108", so here you need to replace $1 with $ {1} to avoid confusion.

echo preg_replace_callback('/^(\w{8})(\w{2})/i',create_function(        // single quotes are essential here,        // or alternative escape all $ as \$        '$matches',        'return $matches[1].\'08\';'    ),$subject);

In this way, callback Processing