(PHP 5 >= 5.1.0, PHP 7, PHP 8)
time_sleep_until — Make the script sleep until the specified time
   Makes the script sleep until the specified
   timestamp. 
  
timestampThe timestamp when the script should wake.
   If the specified timestamp is in the past, this
   function will generate a E_WARNING.
  
Example #1 A time_sleep_until() example
<?php
//returns false and generates a warning
var_dump(time_sleep_until(time()-1));
// may only work on faster computers, will sleep up to 0.2 seconds
var_dump(time_sleep_until(microtime(true)+0.2));
?>Note: All signals will be delivered after the script wakes up.