php正则表达式检测索引级别

Question

I had a look at regular expressions in PHP but I don't really understand how they work.

I have various strings like "1-title" , "1-1-secondTitle", "1-2-otherTitle", This goes up to three level ("1-2-1-text"), so on every string I have this formating and I would like to check if there is one, two or three number before the string starts and then output "0", "1" or "2".

So to make it clearer

"1-index" should return "0"

"3-1-text" should return "1"

"5-2-1-otherTitle" should return "2"

is it possible to check the number of char before the first letter on a string?

Answer 1

Alternaatively, if you dont want to use regex, then, you could just iterate thru the string and overwrite the index. Consider this example:

$string = '5-2-1-otherTitle';
$string = str_ireplace('-', '', $string);
$index = null;
for($x = 0; $x < strlen($string); $x++) {
    if(is_numeric($string[$x])) {
        $index = $x;
    }
}

echo $index; // outputs 2

// works
// echo preg_match_all("/[0-9]/", $string) - 1;