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PHP Basics

Object Oriented Programming

PHP 4/5 Differences

  • Object Orientation
  • E_STRICT – In PHP 5 a new error level E_STRICT is available. As E_STRICT is not included within E_ALL you have to explicitly enable this kind of error level. Enabling E_STRICT during development has some benefits. STRICT messages will help you to use the latest and greatest suggested method of coding, for example warn you about using deprecated functions.
  • References vs. Object Handles | Further Reading

Streams and Network Programming

Security

Functions

Databases and SQL

Strings and Patterns

Arrays

XML and Web Services

Web Features

Design and Theory

Reference

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Reset Webmin Password for ubuntu


I found this problem at the first time when webmin installed. Also this happens to everyone at one time or another. You go on vacation and when you come back, you forget all of the passwords on your computer.

I failed logging in several times and then Webmin blocked my IP. Getting localhost blocked isn’t a good thing to see. So I searched the Internet for a way to reset the password and I found this procedure:

1. Login to your computer as root. Type on browser address bar https://localhost:10000/
2. If you are running a Debian distribution (ubuntu), enter the following command:
/usr/share/webmin/changepass.pl /etc/webmin username password
3. Login to Webmin with your reset password.
4. eNjoY!

How to determine if the user is viewing the Joomla front page or not?


If you are using Joomla older version like 1.0 then you’ll only need to verify the current component with the following command:


if ($option == 'com_frontpage' || $option == '') {
echo 'This is the front page';
}

Bellow porsion for Joomla! 1.5 could be easily confirmed by the following command:


if ( JRequest::getVar('view') === 'frontpage' ) {
echo 'This is the front page';
}

Just in case the above command doesn’t work then the issue could be a little more complicated and need to check if the current active menu item is the default one. I saw this issue in some 1.5 early versions.


$menu =& JSite::getMenu();
if ($menu->getActive() == $menu->getDefault()) {
echo 'This is the front page';
}

Ubuntu Linux Start / Restart / Stop Apache Web Server & MySQL Server


How do I start, restart or stop Apache 2 web server & MySQL server under Ubuntu Linux operating systems?

/etc/init.d/apache2 is service script used to start / stop / restart the Apache2 service under Debian or Ubuntu Linux. You need to login as root or use sudo command restart Apache.
sudo -i
Enter your root password
Task: Start Apache 2 Server
# /etc/init.d/apache2 start
or
$ sudo /etc/init.d/apache2 start

Task: Restart Apache 2 Server
# /etc/init.d/apache2 restart
or
$ sudo /etc/init.d/apache2 restart

Task: Stop Apache 2 Server
# /etc/init.d/apache2 stop
or
$ sudo /etc/init.d/apache2 stop

Task: Start MySQL Server
# /etc/init.d/mysql start
or
$ sudo /etc/init.d/mysql start

Task: Restart MySQL Server
# /etc/init.d/mysql restart
or
$ sudo /etc/init.d/mysql restart

Task: Stop MySQL Server
# /etc/init.d/mysql stop
or
$ sudo /etc/init.d/mysql stop

How to make jQuery work on the same page with Mootools and or Prototype?


Recently i have faced thats problem on my project. Several of my pages use both JQuery and Protoype. Also i have used Mootools some pages. JQuery this appears to be causing problems, because both libraries define a function named ‘$’.

JQuery provides a function noConflict() which relinquishes control of $ to other libraries that may be using it. So it seems like I need to go through all my pages that look like this:

src=”js/mootools.js”

src=”js/prototype.js”
src=”js/jquery.js”

and change them to look like this:

src=”js/mootools.js”

src=”js/prototype.js”
src=”/obp/js/jquery.js”
jQuery.noConflict();
var $j = jQuery;

I should then be able to use ‘$’ for Prototype and ‘$j’ (or ‘jQuery’) for JQuery. I’m not entirely happy about duplicating these 2 lines of code in every relevant page, and expect that at some point somebody is likely to forget to add them to a new page. I’d prefer to be able to do the following

  • Create a file jquery-noconflict.js which “includes” jquery.js and the 2 lines of code shown above
  • Import jquery-noconflict.js (instead of jquery.js) in all my JSP/HTML pages

An alternate solution is simply to add the 2 lines of code above to jquery.js directly, but if I do that I’ll need to remember to do it every time I upgrade JQuery.

Really Easy Field validation with Prototype


Here’s a form validation script that is very easy to use.

Really Easy Field validation with Prototype

Instructions

The basic method is to attach to the form’s onsubmit event, read out all the form elements’ classes and perform validation if required. If a field fails validation, reveal field validation advice and prevent the form from submitting.

Include the javascript libraries:

You write elements like this:

passing the validation requirements in the class attribute.

You then activate validation by passing the form or form’s id attribute like this:>

new Validation(‘form-id’); // OR new Validation(document.forms[0]);

</p

It has a number of tests built-in but is extensible to include your custom validation checks.

The validator also avoids validating fields that are hidden or children of elements hidden by the CSS property display:none. This way you can give a field the class of ‘required’ but it’s only validated if it is visible on the form. The demo illustrates what I am talking about

Options

Here’s the list of classes available to add to your field elements:

  • required (not blank)
  • validate-number (a valid number)
  • validate-digits (digits only)
  • validate-alpha (letters only)
  • validate-alphanum (only letters and numbers)
  • validate-date (a valid date value)
  • validate-email (a valid email address)
  • validate-url (a valid URL)
  • validate-date-au (a date formatted as; dd/mm/yyyy)
  • validate-currency-dollar (a valid dollar value)
  • validate-selection (first option e.g. ‘Select one…’ is not selected option)
  • validate-one-required (At least one textbox/radio element must be selected in a group – see below*)

*To use the validate-one-required validator you must first add the class name to only one checkbox/radio button in the group (last one is probably best) and then place all the input elements within a parent element, for example a div element. That way the library can find all the checkboxes/radio buttons to check and place the validation advice element at the bottom of the parent element to make it appear after the group of checkboxes/radio buttons.

When the validation object is initialised you can pass the option {stopOnFirst : true} to enable the stop on first validation failure behaiour. The demo above has this set to false which is the default. If set to true only the first validation failure advice will be displayed when the form is submitted instead of all at once.

new Validation(‘form-id’,{stopOnFirst:true});

You can also pass the option {immediate : true} to enable field valiation when leaving each field. That is on the onblur event for all the form elements.

By default the library will add an event listener to the form’s onsubmit event and stop the event if the validation fails. If you pass the option {onSubmit : false} it wont do that. This way you can call the validate function manually within your own javascript.

By default the library will focus on the first field that contains an error. If you pass the option {focusOnError : false} it wont do that.

You can also pass the option {useTitles : true} to make the field validators use the form elements’ title attribute value as the error advice message.

You can set callbacks by using the options {onFormValidate : yourFunction, onElementValidate : yourFunction}.

onFormValidate is called after form validation takes place and takes two arguments: the validation result (true or false) and a reference to the form. OnElementValidate is called after each form element is validated and also takes 2 arguments: the validation result (true or false) and a reference to the form element.

Instead of using the error message in the validator you can create your own validation advice page element. Now when the script is creating the advice element it first looks for an element with an id matching ‘advice-‘ + validation-class-name + ‘-‘ + element.id and if not found then one matching ‘advice-‘ + element.id . If your form element does not have an id attribute then match the name attribute. If it finds an element it will make that one appear. See the ‘Donation’ field in the demo for an example. If you make a custom validation advice element make sure you set the style to display : none .

Also if you reference the effects.js file from Scriptaculous in your page head, it’ll use a fade-in effect for the validation advice.

CSS Hooks

As well as the validation css classes above, the validation library uses CSS classes to indicate validation status:

validation-failed and validation-passed

The validation advice element has a class of validation-advice and an id matching the following pattern

‘advice-‘ + validation-class-name + ‘-‘ + element.id

so if the field ‘ birthdate’ uses the ‘ validate-date’ validation class then the validation advice element will have an id of ‘ advice-validate-date-birthdate’.

Select random value from MySQL database table.


The simplest way of selecting random rows from the MySQL database is to use “ORDER BY RAND()” clause in the query.

Solution 1 [SQL QUERY]

SELECT * FROM `table` ORDER BY RAND() LIMIT 0,4;

This query select 4 random value every refresh?

The problem with this method is that it is very slow. The reason for it being so slow is that MySQL creates a temporary table with all the result rows and assigns each one of them a random sorting index. The results are then sorted and returned.

There are several workarounds to speed things up.

The basic idea is to get a random number and then select a specific row using this number.

In the case that all the rows have unique ids we will just have to pick a random number between the smallest and the biggest id and then select the row with id that equals that number. To make this method work when ids are not evenly distributed we will have to use “>=” operator instead of “=” in the last query.

To get the minimum and maximum id values in the entire table we will use MAX() and MIN() aggregate functions. These functions will return minimum and maximum value in the specified group. The group in our case is all the values of `id` column in our table.

Solution 2 [PHP]

$range_result = mysql_query( ” SELECT MAX(`id`) AS max_id , MIN(`id`) AS min_id FROM `table` “);

$range_row = mysql_fetch_object( $range_result );

$random = mt_rand( $range_row->min_id , $range_row->max_id );

$result = mysql_query( ” SELECT * FROM `table` WHERE `id` >= $random LIMIT 0,1 “);

As we mentioned this method is limited to tables with unique id for each row. What to do if it’s not the case?

The solution is to use the MySQL LIMIT clause. LIMIT accepts two arguments. The first argument specifies the offset of the first row to return, and the second specifies the maximum number of rows to return. The offset of the initial row is 0 (not 1).

To calculate the offset to the first row we will generate a random number between 0 and 1 using MySQL’s RAND() function. Then we will multiply this number by number of records in the table, which we will get using COUNT() function. Since LIMIT arguments must be integers and not float values we will round the resulting number using FLOOR() function. FLOOR() is an arithmetic function that calculates the largest integer value that is smaller than or equal to the expression. The resulting code will look like this:

Solution 3 [PHP]

$offset_result = mysql_query( ” SELECT FLOOR(RAND() * COUNT(*)) AS `offset` FROM `table` “);

$offset_row = mysql_fetch_object( $offset_result );

$offset = $offset_row->offset;

$result = mysql_query( ” SELECT * FROM `table` LIMIT $offset, 1 ” );

In MySQL 4.1 and later we can combine two previous methods using subquery like so:

Solution 4 [SQL]

SELECT * FROM `table` WHERE id >= (SELECT FLOOR( MAX(id) * RAND()) FROM `table` ) ORDER BY id LIMIT 1;

This solution has the same weakness as the solution 2 e.g. it only works for tables with unique ids.

Remember the reason we started looked for alternative ways of selecting random rows? Speed! So how do these methods compare in terms of execution times. I am not going to go into specifics of hardware and software configuration or give precise numbers. The approximate results are:

  • The slowest method is solution 1. Let’s say that it took 100% of time to execute.
  • Solution 2 took 79%.
  • Solution 3 – 13%.
  • Solution 4 – 16%.

The winner is solution 3.