(PHP 4, PHP 5)
sleep — Delay execution
$seconds
   )
   Delays the program execution for the given number of
   seconds.
  
secondsHalt time in seconds.
   Returns zero on success, or FALSE on error.
  
   If the call was interrupted by a signal, sleep() returns
   a non-zero value. On Windows, this value will always be
   192 (the value of the
   WAIT_IO_COMPLETION constant within the Windows API).
   On other platforms, the return value will be the number of seconds left to
   sleep.
  
   If the specified number of seconds is negative,
   this function will generate a E_WARNING.
  
| Version | Description | 
|---|---|
| 5.3.4 | Before PHP 5.3.4, on Windows, sleep() always
        returns NULLwhen sleep has occurred, regardless of whether the
        sleep was interrupted or not. | 
Example #1 sleep() example
<?php
// current time
echo date('h:i:s') . "\n";
// sleep for 10 seconds
sleep(10);
// wake up !
echo date('h:i:s') . "\n";
?>
This example will output (after 10 seconds)
05:31:23 05:31:33