PHP Strings Extracting Substrings

PHP Strings

Extracting Substrings

Problem

You want to extract part of a string, starting at a particular place in the string. For example, you want the first eight characters of a username entered into a form.

Solution

Example  Extracting a substring with substr( )

         $substring = substr($string,$start,$length);

         $username = substr($_GET['username'],0,8);

Discussion

If $start and $length are positive, substr() returns $length characters in the string, starting at $start. The first character in the string is at position 0.

Example  Using substr( ) with positive $start and $length

         print substr('watch out for that tree',6,5);

Example   prints:

         out f

If you leave out $length, substr() returns the string from $start to the end of theoriginal string

Example  Using substr( ) with positive start and no length

         print substr('watch out for that tree',17);

Example  prints:

         t tree

If $start is bigger than the length of the string, substr() returns false. If $start plus $length goes past the end of the string, substr() returns all of the stringfrom $start forward

Example  Using substr( ) with length past the end of the string

         print substr('watch out for that tree',20,5);

Example  prints:

         ree

If $start is negative, substr() counts back from the end of the string to determine

where your substring starts

Example  Using substr( ) with negative start

         print substr('watch out for that tree',-6);

         print substr('watch out for that tree',-17,5);

Example  prints:

         t tree

        out f

With a negative $start value that goes past the beginning of the string (for example, if

$start is −27 with a 20-character string), substr() behaves as if $start is 0. If $length is negative, substr() counts back from the end of the string to determine

where your substring ends

Example  Using substr( ) with negative length

        print substr('watch out for that tree',15,-2);

        print substr('watch out for that tree',-4,-1);

Example  prints:

        hat tr

       tre