
Let me explain how it works, so at least you know 
<?php
$host = $_SERVER['SERVER_NAME'] . $_SERVER['REQUEST_URI'];
if(strpos(strtolower($host), 'www.mysiteoo.com/') !== false
|| strpos(strtolower($host), 'www.mysiteoo.com/es/') !== false)
{
echo $this->__('<div class="col-left-banner sidebar">');
} else {
echo $this->__('<div class="col-left sidebar">');
}
?>
Okay, so you know how the $host variable is being generated (as that was your original code)
[fphp]strpos[/fphp] is a neat function, think of it like indexOf in other languages (.NET, Java, etc). In short, it takes your input ($host), and looks for a string stored within it (‘www.mysiteoo.com/’). Since the string we are looking for is all lowercase, I forced the $host variable to be lowercase too (I believe there is a stripos function, that is case-insensitive, but I forgot to look it up (just looked it up, and there is, so you could use that instead of doing the strtolower()).
So you could use (assuming you are on PHP 5):
<?php
$host = $_SERVER['SERVER_NAME'] . $_SERVER['REQUEST_URI'];
if(stripos($host, 'www.mysiteoo.com/') !== false
|| stripos($host, 'www.mysiteoo.com/es/') !== false)
{
echo $this->__('<div class="col-left-banner sidebar">');
} else {
echo $this->__('<div class="col-left sidebar">');
}
?>
Anyway, the important thing about strpos and stripos is that you can get a value of 0 and it is VALID! It simply means the string you were searching for was found at the beginning of the input. Otherwise, it will return the index of where that string started/was found.
Consider the following examples:
$host = 'http://www.mysiteoo.com/';
var_dump(stripos($host, 'www.mysiteoo.com/')); // should show 7
$host = 'www.mysiteoo.com/';
var_dump(stripos($host, 'www.mysiteoo.com/')); // should show 0
If you simply checked if (strpos($host, ‘www.mysiteoo.com/’)), and $host was equal to ‘www.mysiteoo.com/’, the IF statement would return FALSE because 0 is FALSE. So you have to use a strict condition !== false so it accepts 0 as being a result for TRUE.
Hope this helps, and if any of it needs further explanation, just let me know.