ZEND PHP 5 Certification STUDY GUIDE

92 ” Strings And Patterns
Sub-Expressions
A sub-expression is a regular expression contained within the main regular expression
(or another sub-expression); you define one by encapsulating it in parentheses:
/a(bc.)e/
This expression will match the letter a, followed by the letters b and c, followed by
any character and, finally the letter e. As you can see, sub-expressions by themselves
do not have any influence on the way a regular expression is executed; however, you
can use them in conjunction with quantifiers to allow for complex expressions to
happen more than once. For example:
/a(bc.)+e/
This expression will match the letter a, followed by the expression bc. repeated one
or more times, followed by the letter e.
Sub-expressions can also be used as capturing patterns, which we will examine in
the next section.
Matching and Extracting Strings
The preg_match() function can be used to match a regular expression against a given
string. The function returns integer 1 if the match is successful, and can return all
the captured subpatterns in an array if an optional third parameter is passed by reference.
Here’s an example:
$name = "Davey Shafik";
Licensed to 482634 - Amber Barrow (itsadmin@deakin.edu.au)
// Simple match
$regex = "/[a-zA-Z\s]/";
if (preg_match($regex, $name)) {
// Valid Name
}
// Match with subpatterns and capture