Programming PHP

The c in strcspn( ) stands for complement—it tells you how much of the start of the
string is not composed of the characters in the character set. Use it when the number of
interesting characters is greater than the number of uninteresting characters. For example,
this function tests whether a string has any NUL-bytes, tabs, or carriage returns:
function has_bad_chars ($str) {
return strcspn($str, "\n\t\0");
}
Decomposing URLs
The parse_url( ) function returns an array of components of a URL:
$array = parse_url(url);
For example:
$bits = parse_url('http://me:secret@example.com/cgi-bin/board?user=fred);
print_r($bits);
Array
(
[scheme] => http
[host] => example.com
[user] => me
[pass] => secret
[path] => /cgi-bin/board
[query] => user=fred
)
The possible keys of the hash are scheme, host, port, user, pass, path, query, and
fragment.
Regular Expressions
If you need more complex searching functionality than the previous methods provide,
you can use regular expressions. A regular expression is a string that represents
a pattern. The regular expression functions compare that pattern to another string
and see if any of the string matches the pattern. Some functions tell you whether
there was a match, while others make changes to the string.
PHP provides support for two different types of regular expressions: POSIX and Perlcompatible.
POSIX regular expressions are less powerful, and sometimes slower,
than the Perl-compatible functions, but can be easier to read. There are three uses for
regular expressions: matching, which can also be used to extract information from a
string; substituting new text for matching text; and splitting a string into an array of
smaller chunks. PHP has functions for all three behaviors for both Perl and POSIX
regular expressions. For instance, ereg( ) does a POSIX match, while preg_match( )
does a Perl match. Fortunately, there are a number of similarities between basic
POSIX and Perl regular expressions, so we’ll cover those before delving into the
details of each library.
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Regular Expressions | 95