Posts Tagged with "tricks"

Sometimes you might want to purge a set of similar Redis keys in one shot. So far, standard Redis "DEL" command does not allow to remove keys using patterns. However, there is a trick to do this action. Execute the following command in bash:

redis-cli -h [host] -p [port] KEYS "prefix:*" | xargs redis-cli DEL

Seems clear? Wait a minute! What if you use multiple databases (keyspaces) and need to remove keys from a database different from default (0) one? No problem there! Here is the solution:

This post will continue one of my previous posts Reading file list from a mapped Windows network drive.

Recently, I have had a challenge with reading files from a directory using a wildcard pattern (i.e. " *.jpg "). Obviously, regular is_file() or file_exists() functions do not work in this case. So, I started looking for a solution that could help me with my problem.

Luckily, there is a function glob() that searches for the pathnames matching given pattern.

<?php
foreach(glob('*.jpg') as $image) {
  if( !is_dir($image) ) {
    $images[] = $image;
  }
}
?>

If you are looking for a method to trim leading and trailing white spaces in all elements of a PHP array, you could use the following code:

<?php
// custom function to trim value
function _trim(&$value) 
{
    $value = trim($value);    
}

$data = array('  a  ',' b',' c   d ');
array_walk($data,"_trim");

var_dump($data);

/*
Output:
array (size=3)
  0 => string 'a' (length=1)
  1 => string 'b' (length=1)
  2 => string 'c   d' (length=5)

*/

This works, but might look a little long. If you want a shorter solution, here it is:

Web developers often need to get visitor's IP address to use it in web applications. This can be used in internal traffic analytics tools, or as a part of security measures.

Most common and standard method of getting visitor's IP address is getting the value "REMOTE_ADDR" from the global PHP array $_SERVER:

<?php
$visitor_ip = $_SERVER['REMOTE_ADDR'];

However, standard PHP $_SERVER['REMOTE_ADDR'] value not necessarily contains the originating visitor's IP address because, for example, visitor can use a proxy server to access your web site. Using PHP we could try to detect user's IP address even if he uses proxy, but keep in mind that there is no guarantee that IP address that you get is 100% accurate (e.g. proxy can be anonymous).

Last week I ran into a situation when I had to read directory file list from a mapped Windows network drive. At your very first look it may seem pretty simple. It is! However, there is a little trick - Windows may require your network/domain credentials, and then standard PHP functions such as opendir() won't be able to access the directory. Fortunately, the solution is pretty simple:

From time to time we create HTML/CSS templates where we need to center a div or an image. For some newbies it poses a problem. In this blog post I'll show you one of the ways of CSS centering.

Suppose you have a div or an image (with the size 150px X 100px) that should be centered on the web page. First step you do is the following CSS:

centered {
  position:  fixed;
  top:  50%;
  left:  50%;
}