The value of value (pun intended) should be encapsulated in quotes (value=a b is not valid, value="a b" is).

Also, make sure to defend against Cross-Site Scripting:

echo '<option value="' . htmlspecialchars($getClient['company_name']) . '">';
echo htmlspecialchars($getClient['company_name']);
echo '</option>';

when you echo it out, it will look something like this...

<tagName attribute=property with spaces>

So the words with spaces are treated as other attributes in HTML. You need to add quotes around the property value like this:

echo "<option value='$getClient[company_name]'>$getClient[company_name]</option>";

PHP don't ignores it. Really PHP don't get it!

value=x y is interpreted as value=x and property y without value.
You should use qoutes to show browser what is correct atribute value

use trim function to remove white space.