(PHP 5 >= 5.3.0)
pcntl_sigprocmask — Sets and retrieves blocked signals
$how
   , array $set
   [, array &$oldset
  ] )
   The pcntl_sigprocmask() function adds, removes or sets blocked
   signals, depending on the how parameter.
  
howSets the behavior of pcntl_sigprocmask(). Possible values:
SIG_BLOCK: Add the signals to the
         currently blocked signals.SIG_UNBLOCK: Remove the signals from the
         currently blocked signals.SIG_SETMASK: Replace the currently
         blocked signals by the given list of signals.setList of signals.
oldset
       The oldset parameter is set to an array
       containing the list of the previously blocked signals.
      
   Returns TRUE on success or FALSE on failure.
  
Example #1 pcntl_sigprocmask() example
<?php
pcntl_sigprocmask(SIG_BLOCK, array(SIGHUP));
$oldset = array();
pcntl_sigprocmask(SIG_UNBLOCK, array(SIGHUP), $oldset);
?>