We have seen blank screen issue a few times in Magento. It seems to be a problem that is fairly common. There are a few ways to debug this and a few potential causes. The absolute first thing you must do is view your PHP information and ensure that that display_errors and error_log is defined.

How to view PHP configuration

To view your PHP configuration you can upload a file named phpinfo.php with the following data and then view the file in your browser:

Once logging and display errors is enabled, then the reason for the error will should log in your PHP error log and then you can take steps to resolve it.

What if there are no error logs?

Magento has its own error handler located at [Magento root]/app/code/core/Mage/Core/Functions.php defined by the function mageCoreErrorHandler(). Sometimes this custom error handler will fail to output the error. The most likely cause of this is when the script runs out of memory.

To ensure there is sufficient memory look at your PHP information for the max_memory field and ensure it is set to at least 256MB. Whatever its current settings try to raise it and test.

Some other potential resolutions including:

• Deleting the cache- execute rm -rf [Magento root]/var/cache/ to delete the cache
• Ensure file permissions are correct
• Ensure the short_open_tag is enabled just in case your theme uses this

If you ever experience issues with extensions you should look at the Magento extension conflict extension which can help resolve rewrite conflicts.

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Quick Extension Overview

I would guess that 30% of stores leave the default Magento favicon. Changing this is quite important as many stores are using the default icon which means your store has nothing to differentiate itself. Follow this guide to change your favicon.

What is a favicon?

You might asking what a favicon is. It is the image that is displayed in the browser tab when accessing your site and it is also displayed when a user bookmarks your site. Here is the favicon of Extendware:

Notice the small yellow graphic in the top left corner of the browser tab? That is the favicon.

How to change the favicon

Changing the favicon is simple. Just follow these steps:

1. Click System -> Configuration in the backend of your store
2. In the left hand menu click Design
3. Click the HTML Head fieldset and you will see a form like the following:
   

To change the favicon simply click the “Browse” button for the Favicon Icon field and upload a new image. The new image must be 16px by 16px or 32px by 32px.

Sometimes Magento will display a “Service Temporarily Unavailable” message. The message will look like the following:

The most common cause of this issue is a file located at [Magento root]/maintenance.flag. If this file exists, then Magento will display this message. The purpose of the file is to put the store into maintenance mode when doing maintenance. However, if someone forgets to delete it, then it will continue to display the message even after maintenance. To resolve, simply delete this file.

If you are looking for an easy way to put your site into maintenance mode while still making it accessible to designers / administrators, then you should get our Magento maintenance mode extension.

Adding Magento meta title / description to your store should be one of the first things you do after installing Magento. To do this is very simple:

What is meta information?

Meta information is important because it is one of the things bots such as Google look at your site to determine page relevancy. In addition, the meta title is especially important because this is the data the browser displays in the title bar / tab when viewing your store.

How to change default meta information

1. Click System -> Configuration in the backend of your store
2. In the left hand menu click Design
3. Click the HTML Head fieldset and you will see a form like the following:
   

To change the default meta data for your store you will want to edit the Default Title, Default Keywords, and Default Description.

Normally your store will display a logo so that your business can be identified. Sometimes it is necessarily to change this especially if you are just creating your first store. To do this is fairly simple if you follow these steps.

1. Go to System -> Configuration in your backend.
2. Click on Design in the left menu.
3. Click on the Header fieldset.

You will see some form fields that look like this:

You will notice you can change the alt text (the text displayed when the mouse hovers over the logo) by changing the Logo Alt Img field. To change the path to the image file you will need to change the Logo Image Src field.

The logo image src will be relative to your skin directory. By default, the magento skin directory is [Magento root]/skin/frontend/base/default/. So, if your logo src is images/logo.png it would need to be located at [Magento root]/skin/frontend/base/default/images/logo.png

Magento includes a database abstraction layer and object relationship manager that is really great at ensuring data integrity and consistent data access. In general, you should avoid writing to the database and instead use a well-written Magento extension that performs the task for you. However, sometimes a direct query needs to be made whether for performance or convenience and in this case you need to know how to do direct queries the right way.

Step 1: Get the database connection

To get the database connection, so you can execute the direct query you should use one of the following depending on whether you need to read or write:

Step 2: Get the table names

Almost every SQL query will require the use of a table name. Magento tables can be prefixed, so it is important to not hardcode the table name. There are two methods to get a table name that will include the prefix:

Get the table name from an entity

Get the table name from a string

Step 3: Reading from a table

Now that we have the read connection and table name we are ready to read from a table. It is oftentimes much faster to perform a direct read of a Magento database, than to the load the object property. In this example we will read the product table in get all products with their ID and SKU:

Step 4: Writing to a table

Just as direct reading can be faster, so can direct writing. Sometimes much faster. Here is a simple example of how to update the SKU of a product with the ID of 1:

Conclusion

Direct reading / writing can be faster or more convenient than using Magento models. However, it is important to do it with cautsion especially when doing direct writing. Magento models ensure data integrity and allow triggers that do things like the Magento full page cache or Magento indexing. Directly writing can create unforeseen issues.

What is Form Validation?

When we say form validation we specifically mean client-side Javascript form validation. Have you ever filled out a Magento from and been told that a specific field is incomplete or includes bad data? That is form validation. This graphic might look familiar to you:

How does Magento perform form validation?

Magento utilizes the Javascript library called Prototype to do this. Specifically, the file [Magento root]/js/prototype/validation.js is where the magic happens. Looking around line 414 you can see the list of validation CSS class names and their error messages. An example of this is:

A full list of all Magento CSS validatoin classes and their error messages is found at the end of the post.

How to use the CSS validation classes to validate your custom forms

All you need to do is reference the validation CSS class in the input type in order to make your forms validate. For example:

Full list of Magento CSS validation classes

• validate-no-html-tags – HTML tags are not allowed
• validate-select – Please select an option.
• required-entry – This is a required field.
• validate-number – Please enter a valid number in this field.
• validate-number-range – The value is not within the specified range.
• validate-digits – Please use numbers only in this field. Please avoid spaces or other characters such as dots or commas.
• validate-digits-range – The value is not within the specified range.
• validate-alpha – Please use letters only (a-z or A-Z) in this field.
• validate-code – Please use only letters (a-z), numbers (0-9) or underscore(_) in this field, first character should be a letter.
• validate-alphanum – Please use only letters (a-z or A-Z) or numbers (0-9) only in this field. No spaces or other characters are allowed.
• validate-alphanum-with-spaces – Please use only letters (a-z or A-Z), numbers (0-9) or spaces only in this field.
• validate-street – Please use only letters (a-z or A-Z) or numbers (0-9) or spaces and # only in this field.
• validate-phoneStrict – Please enter a valid phone number. For example (123) 456-7890 or 123-456-7890.
• validate-phoneLax – Please enter a valid phone number. For example (123) 456-7890 or 123-456-7890.
• validate-fax – Please enter a valid fax number. For example (123) 456-7890 or 123-456-7890.
• validate-date – Please enter a valid date.
• validate-email – Please enter a valid email address. For example [email protected].
• validate-emailSender – Please use only visible characters and spaces.
• validate-password – Please enter 6 or more characters. Leading or trailing spaces will be ignored.
• validate-admin-password – Please enter 7 or more characters. Password should contain both numeric and alphabetic characters.
• validate-cpassword – Please make sure your passwords match.
• validate-url – Please enter a valid URL. Protocol is required (http://, https:// or ftp://)
• validate-clean-url – Please enter a valid URL. For example http://www.example.com or www.example.com
• validate-identifier – Please enter a valid URL Key. For example “example-page”, “example-page.html” or “anotherlevel/example-page”.
• validate-xml-identifier – Please enter a valid XML-identifier. For example something_1, block5, id-4.
• validate-ssn – Please enter a valid social security number. For example 123-45-6789.
• validate-zip – Please enter a valid zip code. For example 90602 or 90602-1234.
• validate-zip-international – Please enter a valid zip code.
• validate-date-au – Please use this date format: dd/mm/yyyy. For example 17/03/2006 for the 17th of March, 2006.
• validate-currency-dollar – Please enter a valid $ amount. For example $100.00.
• validate-one-required – Please select one of the above options.
• validate-one-required-by-name – Please select one of the options.
• validate-not-negative-number – Please enter a number 0 or greater in this field.
• validate-zero-or-greater – Please enter a number 0 or greater in this field.
• validate-greater-than-zero – Please enter a number greater than 0 in this field.
• validate-state – Please select State/Province.
• validate-new-password – Please enter 6 or more characters. Leading or trailing spaces will be ignored.
• validate-cc-number – Please enter a valid credit card number.
• validate-cc-type – Credit card number does not match credit card type.
• validate-cc-type-select – Card type does not match credit card number.
• validate-cc-exp – Incorrect credit card expiration date.
• validate-cc-cvn – Please enter a valid credit card verification number.
• validate-ajax –
• validate-data – Please use only letters (a-z or A-Z), numbers (0-9) or underscore(_) in this field, first character should be a letter.
• validate-css-length – Please input a valid CSS-length. For example 100px or 77pt or 20em or .5ex or 50%.
• validate-length – Text length does not satisfy specified text range.
• validate-percents – Please enter a number lower than 100.
• required-file – Please select a file
• validate-cc-ukss – Please enter issue number or start date for switch/solo card type.