formatting - Adding leading 0 in php

Question

I have

• tutorial 1 how to make this
• tutorial 21 how to make this
• tutorial 2 how to make this
• tutorial 3 how to make this

and i need

• tutorial 01 how to make this
• tutorial 21 how to make this
• tutorial 02 how to make this
• tutorial 03 how to make this

so i can order them properly. (adding leading 0 when single digit is found)

What would be a php method to convert?

thanks in advance

note-please make sure that it identifies the single digit numbers only first and then add the leading zero

Answer 1

str_pad()

echo str_pad($input, 2, "0", STR_PAD_LEFT);

sprintf()

echo sprintf("%02d", $input);