Added PHP API for registering tick functions. Ticks is a per-instruction
callback in Zend that allows us to implement cooperative multitasking
within PHP. Example:
In extension code:
php_add_tick_function(my_tick_func);
void my_tick_func(int count) {
php_printf("[tick %d]", count);
}
In PHP code:
<?php
declare(ticks = 1) {
print "there should be two ticks here.\n";
}
?>
Draft 3 of IEEE 1003.1 200x, "2.2 The Compilation Environment"
All identifiers that begin with an underscore and either an uppercase
letter or another underscore are always reserved for any use by the
implementation.
