[0-9] + .txt似乎不匹配带有数字名称的文本文件

This pattern doesn't appear to be correctly matching txt files with numeric names: [0-9]+.txt.
Can someone advise me as to what I'm doing wrong?

Context: $posts = preg_grep("[0-9]+.txt", glob('posts/*.txt'));

Your expression is missing the delimiters:

'~/[0-9]+\.txt$~'

But it might just be easier to add this requirement into glob() itself:

$posts = glob('posts/[0-9]*.txt');