title: file_put_contents appending data on a file being written by another process
body: <p>I have</p>
  
  <pre><code>$bytesCount = file_put_contents( "somefile.log", "some text\n", FILE_APPEND | LOCK_EX );
  </code></pre>
  
  <p>What happens if another process is writing** on <code>somefile.log</code>?</p>
  
  <p>Does <code>file_put_contents</code> fails with a runtime error ?</p>
  
  <p>Does if fails with <code>$bytesCount === false</code></p>
  
  <p>Or does does it pause the script until the file is unlocked and then performs the write operation?</p>
  
  <hr>
  
  <p>(**) <em>or more generally another process has an exclusive lock on the file</em></p>
  
  <hr>
  
  <p>[ <em>I'm on a <code>*nix</code> platform with php 5.6</em> ]</p>