"PHP Learning Notes" ticks article

1. What is Ticks

Let's take a look at the handbook's explanation of ticks:

A Tick is an event, occurs for every N low-level statements executed by the parser within the declare block. The value for N is specified using Ticks=n within the Declare block ' s Directive section.

To summarize:

• Tick is an event
• The Tick event is released once per n low-level statements, n is specified by the Declare statement
• Register_tick_function () can be used to specify the time of the Handler,unregister_tick_function () corresponding to the

As for what is low-level statements, do not start here, in summary, low-level statements includes the following situations:
(1) Simple statement: empty statement (one; number), return, break, continue, throw, Goto, Global, Static, unset, Echo, built-in HTML text, semicolon-terminated expression, etc. all count as one statement. (2) Compound statement: Complete If, ElseIf, while, Do...while, for, foreach, switch, try...catch, etc to calculate a statement(3) statement block: {} braces count a block of statements(4) Declare itself is a compound statement

All the statement, function_declare_statement, class_declare_statement constitute the low-level statement.

2. Tick Pits

It is important to note that: Declare () is not a function!!! To be precise, he is talking about a language structure, so there may be some unexpected behavior, for example, when you use declare () in a file many times, the principle of parsing is: Who is in front of me and who I am using recently, completely ignoring your code logic, do not unfold here. One of the suggested uses is

Declare (ticks=10) {for    ($i = 0; $i <; $i + +) {        print "hello\n";    }} Declare (ticks=2) {for    ($i = 0; $i <; $i + +) {        print "hello\n";    }}

3. Application of Tick

When we say so much, when are we going to use tick? In general, tick can be used for debugging, performance testing, simple multitasking or background I/O operations, and so on.

Here, give me a bird. Example provided for complete communication

<?php/* * Use ticks to complete message communication *///create a message Queue$mesg_key = Ftok (__file__, ' m '); $MESG _id = Msg_get_queue ($MESG _key, 0666)//ticks callbackfunction fetchmessage ($mesg _id) {    if (!is_resource ($MESG _id)) {        Print_r ("Mesg Queue is Not ready \ n ");    }    if (msg_receive ($MESG _id, 0, $MESG _type, 1024x768, $MESG, False, msg_ipc_nowait)) {        Print_r ("Process got a new incoming MS G: $MESG \ n ");    }} Register Ticks Callbackregister_tick_function ("Fetchmessage", $mesg _id);//send messages;declare (ticks = 2) {    $i = 0;    while (+ + $i <) {        if ($i% 5 = = 0) {            msg_send ($mesg _id, 1, "Hi:now Index is:". $i);}}}    

Let's take a look at the output:

We found that the tick event was triggered every two statements, due to the registration of the Tick event's callback, thus performing an action to cancel the coupon from the message queue. This simulates the process of sending and receiving messages.