Regex Match Exact Number at beginning (like 99 but not 999) - php

Question

This should be a simple task, but searching for it all day I still can't figure out what I'm missing
I'm trying to open a file using PHP's glob() that begins with a specific number
Example filenames in a directory:
1.txt
123.txt
10 some text.txt
100 Some Other Text.txt
The filenames always begin with a unique number (which is what i need to use to find the right file) and are optionally followed by a space and some text and finally the .txt extension
My problem is that no matter what I do, if i try to match the number 1 in the example folder above it will match every file that begins with 1, but I need to open only the file that starts with exactly 1, no matter what follows it, whether it be a space and text or just .txt
Some example regex that does not succeed at the task:
filepath/($number)*.txt
filepath/([($number)])( |*.?)*.txt
filepath/($number)( |*.?)*.txt
I'm sure there's a very simple solution to this... If possible I'd like to avoid loading every single file into a PHP array and using PHP to check every item for the one that begins with only the exact number, when surely regex can do it in a single action
A bonus would be if you also know how to turn the optional text between the number and the extension into a variable, but that is entirely optional as it's my next task after I figure this one out

Answer 1

The Regex you want to use is: ^99(\D+\.txt)$
$re = "/^99(\D+\.txt)$/";
preg_match($re, $str, $matches);
This will match:
99.txt
99files.txt
but not:
199.txt
999.txt
99
99.txt.xml
99filesoftxt.dat
The ( ) around the \D+.txt will create a capturing group which will contain your file name.

Answer 2

I believe this is what you want OP:
$regex = '/' . $number . '[^0-9][\S\s]+/';
This matches the number, then any character that isn't a number, then any other characters. If the number is 1, this would match:
1.txt
1abc.txt
1 abc.txt
1_abc.txt
1qrx.txt
But it would not match:
1
12.txt
2.txt
11.txt
1.

Answer 3

Here you go:
<?php
function findFileWithNumericPrefix($filepath, $prefix)
{
if (($dir = opendir($filepath)) === false) {
return false;
}
while (($filename = readdir($dir)) !== false) {
if (preg_match("/^$prefix\D/", $filename) === 1) {
closedir($dir);
return $filename;
}
}
closedir($dir);
return false;
}
$file = findFileWithNumericPrefix('/base/file/path', 1);
if ($file !== false) {
echo "Found file: $file";
}
?>
With your example directory listing, the result is:
Found file: 1.txt

Answer 4

You can use a regex like this:
^10\D.*txt$
^--- use the number you want
Working demo
For intance:
$re = "/^10\\D.*txt$/m";
$str = "1.txt\n123.txt\n10 some text2.txt\n100 Some Other2 Text.txt";
preg_match_all($re, $str, $matches);
// will match only 10 some text.txt