(PHP 5 >= 5.3.0, PHP 7, PHP 8)
pcntl_sigprocmask — Sets and retrieves blocked signals
$mode, array $signals, array &$old_signals = null): bool
   The pcntl_sigprocmask() function adds, removes or sets blocked
   signals, depending on the mode parameter.
  
modeSets 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.signalsList of signals.
old_signals
       The old_signals 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);
?>