Question

How can I get all the digits at the beginning of a string?

Here is an example string: 1&days=800&trans=9aq8ojjfka24qnl10ohktibfs1

In the example above, I would need to extract 1.

Answer 1

If you need the leading digits – including mulitple zeros – you can scan the string for it. If none exists, the value will be NULL:

$subject = '1&days=800&trans=9aq8ojjfka24qnl10ohktibfs1';   

sscanf($subject, '%[0-9]', $leadingDigits);

echo 'Leading digits are: ', var_dump($leadingDigits);

Outpupt (Demo):

Leading digits are: string(1) "1"

If you do not need leading zeroes, do what vascowhite suggested, that is pretty straight forward. Otherwise:

sscanf($subject, '%d', $leadingDigits);

Returns an integer, too.