ZEND PHP 5 Certification STUDY GUIDE

Strings And Patterns ” 83
The third argument is our starting point—the space in the first example; the function
replaces the contents of the string from here until the end of the string with the
second argument passed to it, thus resulting in the output Hello Reader. You can
also pass an optional fourth parameter to define the end of the substring that will
be replaced (as shown in the second example, which outputs Canned potatoes are
good).
Combining substr_replace() with strpos() can prove to be a powerful tool. For
example:
$user = "davey@php.net";
$name = substr_replace($user, "", strpos($user, ’@’);
echo "Hello " . $name;
By using strpos() to locate the first occurrence of the @ symbol, we can replace the
rest of the e-mail address with an empty string, leaving us with just the username,
which we output in greeting.
Extracting Substrings
The very flexible and powerful substr() function allows you to extract a substring
from a larger string. It takes three parameters: the string to be worked on, a starting
index and an optional length. The starting index can be specified as either a positive
integer (meaning the index of a character in the string starting from the beginning)
or a negative integer (meaning the index of a character starting from the end). Here
are a few simple examples:
$x = ’1234567’;
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echo substr ($x, 0, 3); // outputs 123
echo substr ($x, 1, 1); // outputs 2
echo substr ($x, -2); // outputs 67
echo substr ($x, 1); // outputs 234567
echo substr ($x, -2, 1); // outputs 6