title: php String Concatenation, Performance
body: <p>In languages like Java and C#, strings are immutable and it can be computationally expensive to build a string one character at a time.  In said languages, there are library classes to reduce this cost such as C# <code>System.Text.StringBuilder</code> and Java <code>java.lang.StringBuilder</code>.</p>
  
  <p>Does php (4 or 5; I'm interested in both) share this limitation?  If so, are there similar solutions to the problem available?</p>