title: PHP associative array's keys (indexes) limitations?
body: <p>If there are some kind of limitations for array keys in PHP ? Length ? Not acceptable strings ?</p>
  
  <p>In the <a href="http://www.php.net/manual/en/language.types.array.php" rel="noreferrer">official documentation</a> found only this, but there is no information about keys limitations.</p>
  
  <blockquote>
    <p>A key may be either an integer or a string. If a key is the standard representation of an integer, it will be interpreted as such (i.e. "8" will be interpreted as 8, while "08" will be interpreted as "08"). Floats in key are truncated to integer. The indexed and associative array types are the same type in PHP, which can both contain integer and string indices.*</p>
  </blockquote>