The `pcntl_alarm` function is used in PHP to generate an alarm signal after a specified number of seconds. This function is part of the PCNTL (Process Control) functions, which are used to handle Unix style process signaling and control in PHP.

**Syntax:**

“`php
int pcntl_alarm ( int $seconds )
“`

**Parameters:**

– `$seconds`: The number of seconds to wait before the alarm signal is generated. If this parameter is set to zero, no new alarm will be created but the old one will be cancelled.

**Return Value:**

This function returns the time in seconds that any previously scheduled alarm had remaining before it was due to be delivered, or zero if there was no previously scheduled alarm.

**Example:**

“`php

“`
In this example, the `pcntl_alarm` function is used to generate an alarm signal every 2 seconds. When the signal is caught by the `sig_handler` function, it outputs “Caught SIGALRM”.

Please note that ticks must be declared in your code for signal handling, otherwise your script may not respond as expected. Ticks are used to determine how often a piece of code should be executed.

Remember that PCNTL functions are not available on Windows platforms, and they may not be present in your PHP installation if they have not been enabled during configuration.