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Web Technologies-I

Notes Example:

// prints “Found ‘cat’”
if (ereg(“cat”, “raining cats and dogs”))
print “Found ‘cat’”;
The regular expression cat matches the subject string, and the fragment prints “Found ‘cat’”.
Characters and Wildcards

To represent any character in a pattern, a period is used as a wildcard. The pattern c. matches
any three-letter string that begins with a lowercase c; for example, cat, cow, cop, and so on. To
express a pattern that actually matches a period, use the backslash character \. For example, .com
matches both .com and xcom but \.com matches’ only .com.
The use of the backslash in a regular expression can cause confusion. To include a backslash in
a double-quoted string, you need to escape the meaning of the backslash with a backslash. The
following example shows how the regular expression pattern “\.com” is represented:
Example:

// Sets $found to true
$found = ereg(“\\.com”, “www.ora.com”);
It is better to avoid the confusion and use single quotes when passing a string as a regular
expression:

$found = ereg(‘\.com’, “www.ora.com”);
Character lists
Rather than using a wildcard that matches any character, a list of characters enclosed in brackets can
be specified within a pattern. For example, to match a three-character string that starts with a “p”,
ends with a “p”, and contains a vowel as the middle letter, you can use the following expression:
ereg(“p[aeiou]p”, $var)

This returns true for any string that contains “pap”, “pep”, “pip”, “pop”, or “pup”. The character
list in the regular expression “p[aeiou]p” matches with exactly one character, so strings like
“paep” do not match. A range of characters can also be specified; for example, “[0-9]” specifies
the numbers 0 through 9:

Example:
// Matches “A1”, “A2”, “A3”, “B1”, ...

$found = ereg(“[ABC][123]”, “A1 Quality”); // true
// Matches “00” to “39”
$found = ereg(“[0-3][0-9]”, “27”); //true
$found = ereg(“[0-3][0-9]”, “42”); //false
A list can specify characters that are not matches using the not operator ^ as the first character
in the brackets. The pattern “[^123]” matches any character other than 1, 2, or 3. The following
examples show regular expressions that make use of the not operator in lists:

Example:

// true for “pap”, “pbp”, “pcp”, etc. but not “php”
$found = ereg(“p[^h]p”, “pap”); //true

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