OS X: replace tabs with spaces in all files using expand

PHP: removing zero values from an array

If you call array_filter without a callback function, it’ll remove all array elements that evaluate to false (including zeroes).

$numbers = array(0, 1, 2, 0);
echo array_filter($numbers);

Produces:

array(1,2);

PHP: returning an array of single attributes from an array of objects

I miss Ruby’s shorthand collect method to return an array of single attributes:

animals.collect(&:name)

…so I’ve created a (less elegant) equivalent for PHP.

class ArrayExtensions
{
    /**
     * From an array of objects, create a new array containing only 
     * a single attribute of each object
     * 
     * Similar to array.collect(&:attribute) in Ruby
     */
    public static function collect_by_attribute($attribute, $array_of_objects)
    {
        if (!is_array($array_of_objects))
        {
            return array();
        }

        $output = array();

        foreach ($array_of_objects as $object)
        {
            if (is_object($object) && isset($object->$attribute))
            {
                $output[] = $object->$attribute;
            }
        } 
        
        return $output;
    }
}

Use it like this:

$colours = ArrayExtensions::collect_by_attribute('colour', $animals);

…and you’ll get a simple array containing just the attribute you’ve specified:

array('brown', 'blue', 'green')

Update

If you happen to be using PHP ActiveRecord, they have a function called collect that will accomplish the same thing.

$colours = ActiveRecord\collect($animals, 'colour');

PHP: check if a PEAR class is installed

You can’t use file_exists because it doesn’t search the include path.

fopen has a third argument that will check the include path, though:

if (@fopen('Log.php', 'r', true)) 
{   
  echo 'It exists!'; 
}

Redirect the output of a command to a file when using sudo

Rather than > or », use tee.

Redirecting the output of commands run with sudo requires a different approach. For instance consider sudo ls > /root/somefile will not work since it is the shell that tries to write to that file. You can use ls | sudo tee -a /root/somefile to append, or ls | sudo tee /root/somefile to overwrite contents.

From https://help.ubuntu.com/community/RootSudo

Subversion branching best practice

Most new code is checked into the trunk.  In general, our developers try to never “break the tree”.  Anyone who checks in code which causes the trunk builds to fail will be the recipient of heaping helpings of trash talk and teasing until he gets it fixed.  The trunk should always build, and as much as possible, the resulting build should always work. Most new code is checked into the trunk. The trunk is the place where active development of new features is happening.  The trunk could be described as “basically unstable”. In our situation, the stability of the trunk build fluctuates over the months during our development cycle. During the early and middle parts of a development cycle, the trunk is often not very stable at all.  As we approach alpha, beta and final release, things settle down and the trunk gets more and more stable. At the moment of release, a branch gets created.  This branch becomes our maintenance tree for that release.  Our current maintenance branch is called “3.0”, since that’s the current major version number of our product.  When we need to do a bug fix or patch release, it is done in the maintenance branch.  Each time we do a release out of the maintenance branch (like 3.0.2), we apply a tag. After the maintenance branch is created, the trunk once again becomes “basically unstable”.  Developers start adding the risky code changes we didn’t want to include in the release.  New feature work begins.  The cycle starts over and repeats itself.

From http://www.ericsink.com/scm/scm_branches.html

List your Apache virtual hosts

apache2ctl -t -D DUMP_VHOSTS

Copy a large directory of files using ls and xargs

ls . | xargs -i -t cp ./{} /path/to/new/directory

See example 12-6 at http://www.homepage.montana.edu/~unixuser/051905/abs-guide/moreadv.html

Rails migrations: creating a MySQL BIGINT

add_column :facebook_user_id, :integer, :limit => 8 # BIGINT

Basic use of ‘screen’

Using screen is a great way to leave long-running processes churning away when you’re not logged into the machine.

Open a new screen

screen

Detach from the screen

This does not interrupt whatever is running in the screen. Press Ctrl-A then D.

Reattach to a screen you’ve already opened

screen -r

If you’ve opened multiple screens, a list will be displayed:

There are several suitable screens on:
	1681.ttys004.braeburn	(Detached)
	1686.ttys004.braeburn	(Detached)

Just use the process ID of the screen to resume the right one:

screen -r 1681