Recipe 1.2 Accessing Substrings
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.
1.2.1 Solution
Use substr( ) to select your substrings:
$substring = substr($string,$start,$length);
$username = substr($_REQUEST['username'],0,8);
1.2.2 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:
print substr('watch out for that tree',6,5);
out f
If you leave out $length, substr(
) returns the string from $start to the
end of the original string:
print substr('watch out for that tree',17);
t tree
If $start plus $length goes
past the end of the string, substr( ) returns all
of the string from $start forward:
print substr('watch out for that tree',20,5);
ree
If $start is negative, substr(
) counts back from the end of the string to determine where
your substring starts:
print substr('watch out for that tree',-6);
print substr('watch out for that tree',-17,5);
t tree
out f
If $length is negative, substr(
) counts back from the end of the string to determine where
your substring ends:
print substr('watch out for that tree',15,-2);
print substr('watch out for that tree',-4,-1);
hat tr
tre
1.2.3 See Also
Documentation on substr( ) at
http://www.php.net/substr.
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