Simple class definition in PHP

Here is a simple class definition in PHP

<?php

class Box {

private $_length;
private $_width;
private $_height;

public function Box($length, $width, $height) {
$this->_length = $length;
$this->_width = $width;
$this->_height = $height;
}

public function volume() {
return $this->_length * $this->width * $this->_height;
}

}

//Example of using the class
$myBox = new Box(20,10, 5);
$myVolume = $myBox->volume();
echo($myVolume);

?>

The definitions of each access modifier :

public. Public members can be accessed both from outside an object by using $obj->publicMember and by accessing it from inside the myMethod method via the special $this variable (for example, $this->publicMember). If another class inherits a public member, the same rules apply, and it can be accessed both from outside the derived class’s objects and from within its methods.

protected. Protected members can be accessed only from within an object’s method—for example, $this->protectedMember. If another class inherits a protected member, the same rules apply, and it can be accessed from within the derived object’s methods via the special $this variable.

private. Private members are similar to protected members because they can be accessed only from within an object’s method. However, they are also inaccessible from a derived object’s methods. Because private properties aren’t visible from inheriting classes, two related classes may declare the same private properties. Each class will see its own private copy, which are unrelated.

Regular Expressions Part 4 – Array Processing

PHP’s preg_split() function enables you to break a string apart basing on something more complicated than a literal sequence of characters. When it’s necessary to split a string with a dynamic expression rather than a fixed one, this function comes to the rescue. The basic idea is the same as preg_match_all() except that, instead of returning matched pieces of the subject string, it returns an array of pieces that didn’t match the specified pattern. The following example uses a regular expression to split the string by any number of commas or space characters:

<?php
‘——————————————————
$keywords = preg_split(“/[\s,]+/”, “php, regular expressions”);
print_r( $keywords );
‘——————————————————
?>

Another useful PHP function is the preg_grep() function which returns those elements of an array that match a given pattern. This function traverses the input array, testing all elements against the supplied pattern. If a match is found, the matching element is returned as part of the array containing all matches. The following example searches through an array and all the names starting with letters A-J:

<?php
‘——————————————————
$names = array(‘Andrew’,’John’,’Peter’,’Nastin’,’Bill’);
$output = preg_grep(‘/^[a-m]/i’, $names);
print_r( $output );
‘——————————————————
?>

Regular Expressions Part 3 – Replacing Patterns

Replacing Patterns

In the examples in Part 2, we have searched for patterns in a string, leaving the search string untouched. The preg_replace() function looks for substrings that match a pattern and then replaces them with new text. preg_replace() takes three basic parameters and an additional one. These parameters are, in order, a regular expression, the text with which to replace a found pattern, the string to modify, and the last optional argument which specifies how many matches will be replaced.
preg_replace( pattern, replacement, subject [, limit ])

The function returns the changed string if a match was found or an unchanged copy of the original string otherwise. In the following example we search for the copyright phrase and replace the year with the current.
<?php
echo preg_replace(“/([Cc]opyright) 200(3|4|5|6)/”, “$1 2007”, “Copyright 2005”);
?>

In the above example we use back references in the replacement string. Back references make it possible for you to use part of a matched pattern in the replacement string. To use this feature, you should use parentheses to wrap any elements of your regular expression that you might want to use. You can refer to the text matched by subpattern with a dollar sign ($) and the number of the subpattern. For instance, if you are using subpatterns, $0 is set to the whole match, then $1, $2, and so on are set to the individual matches for each subpattern.

In the following example we will change the date format from “yyyy-mm-dd” to “mm/dd/yyy”:
<?php
echo preg_replace(“/(\d+)-(\d+)-(\d+)/”, “$2/$3/$1”, “2007-01-25”);
?>

We also can pass an array of strings as subject to make the substitution on all of them. To perform multiple substitutions on the same string or array of strings with one call to preg_replace(), we should pass arrays of patterns and replacements. Have a look at the example:
<?php
$search = array ( “/(\w{6}\s\(w{2})\s(\w+)/e”,
“/(\d{4})-(\d{2})-(\d{2})\s(\d{2}:\d{2}:\d{2})/”);

$replace = array (‘”$1 “.strtoupper(“$2”)’,
“$3/$2/$1 $4”);

$string = “Posted by John | 2007-02-15 02:43:41”;

echo preg_replace($search, $replace, $string);?>

In the above example we use the other interesting functionality – you can say to PHP that the match text should be executed as PHP code once the replacement has taken place. Since we have appended an “e” to the end of the regular expression, PHP will execute the replacement it makes. That is, it will take strtoupper(name) and replace it with the result of the strtoupper() function, which is NAME.