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This article mainly introduces "there is no timer in PHP". In daily operation, I believe many people have doubts about whether there is no timer in PHP. The editor consulted all kinds of data and sorted out simple and easy-to-use methods of operation. I hope it will be helpful to answer the question of "PHP does not have timer?" Next, please follow the editor to study!

PHP doesn't have a timer?

Indeed, PHP does not have native timer-related functions like setInterval or setTimeout in JS. But we can do this in other ways, such as using declare.

Let's take a look at how it is implemented, and then let's take a good look at what an declare expression is.

Function do_tick ($str ='')

{

List ($sec, $usec) = explode ('', microtime ())

Printf ("[.4f] Tick.%s\ n", $sec + $usec, $str)

}

Register_tick_function ('do_tick')

Do_tick ('--start--')

Declare (ticks = 1) {

While (1) {

Sleep (1); / / here, do_tick () is called every time it is executed.

}

}

Very simple code that will output the current time per second when it is run.

The definition of declare syntax is as follows:

Declare (directive)

Statemaent

The declare structure is used to set the execution instruction directive part of a piece of code that allows you to set the behavior of the declare snippet. Currently only two instructions are known: ticks and encodingTick (clock cycle) are events that occur every time the interpreter executes N timed low-level statements in the declare code snippet. The value of N is specified by ticks=N in the directive section of declare, and the events that appear in each tick are specified by register_tick_function ()

Here, we only study the use of ticks.

In the above code, we use register_tick_function () to register the do_tick () method and assign ticks=1 to ticks,declare, that is, each time a timed low-level statement is executed, the method registered in register_tick_function () is executed. Every time the while in the declare block loops, a sleep () pauses for a second, and this sleep () is the low-level statement that can be timed.

So, isn't while () a timed low-level statement? Of course not. Conditional judgments such as where and if are not such timed low-level statements.

Not all statements can be timed. Usually, neither conditional expression nor parameter expression can be timed.

Let's use the following example to see how step-by-step declare is implemented:

Function test_tick ()

{

Static $I = 0

Echo 'test_tick:'. $iTunes, PHP_EOL

}

Register_tick_function ('test_tick')

Test_tick (); / / test_tick:0

$j = 0

Declare (ticks = 1) {

$jacuzzi; / / test_tick:1

$jamboree; / / test_tick: 2

Sleep (1); / / after 1 second stop, test_tick:3

$jacuzzi; / / test_tick:4

If ($j = = 3) {/ / conditional expression, does not execute ticks

Echo "aa", PHP_EOL; / / test_tick:5\ nThe test_tick:6,PHP_EOL accountant once ticks

}

}

/ / declare has no effect using all the code followed by curly braces, and the scope is limited to curly braces.

Echo "bbb" / /

Echo "ccc" / /

Echo "ddd" / /

The notes are so detailed that we don't have to explain them one by one. Let's take a look at the result of setting ticks to 2 and the statemaent under declare without curly braces:

Function test_tick1 ()

{

Static $I = 0

Echo 'test_tick1:'. $iTunes, PHP_EOL

}

Register_tick_function ('test_tick1')

$j = 0; / / No time here

Declare (ticks = 2)

$jacuzzi; / / test_tick1:0

$jacks +

Sleep (1); / / test_tick1:1 after stopping for 1 second

$jacks +

$jacuzzi; / / test_tick1:2

If ($j = = 4) {/ / conditional expression, does not execute ticks

/ / echo "aa", PHP_EOL

Echo "aa"; / / test_tick:10,test_tick1 does not execute and does not jump two steps. If PHP_EOL is used, two steps will be output test_tick1:3

}

/ / if declare does not use curly braces, it will have an effect on all the following code. If it is require or include, it will not deal with the subsequent content of the parent page.

Echo "bbb"; / / test_tick1:3

Echo "ccc"

Echo "ddd"; / / test_tick1:4

As you can see, our declare has an effect on the subsequent code of its definition, but it should be noted that if there is a page nesting, it has no effect on the subsequent code of the parent page. Once ticks=2 is defined, the function code registered by register_tick_function () is executed once after two low-level countable age codes.

Test code: https://github.com/zhangyue0503/dev-blog/blob/master/php/201911/source/PHP%E6%B2%A1%E6%9C%89%E5%AE%9A%E6%97%B6%E5%99%A8%EF%BC%9F.php

Reference document: https://www.php.net/manual/zh/control-structures.declare.php

At this point, the study on "there is no timer in PHP" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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