Detailed explanation of the function of declare in php-PHP Tutorial-php.cn

Detailed explanation of the function of declare in php

伊谢尔伦

Release： 2023-03-11 10:56:01

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declareFunction in

php:

The general usage is declare(ticks=N);
Take declare(ticks=1) as an example. This sentence has two main functions. : 1. Every time the Zend engine executes a low-level statement, it executes the function
registered by register_tick_function(). can be roughly understood as executing the registered tick function every time a sentence of php code
(for example: $num=1;) is executed. One use is to control the execution time of a certain piece of code. For example, although the following code has a dead loop
at the end, the execution time will not exceed 5 seconds.

Run php timeout.php

<?php
declare(ticks=1);
// 开始时间
$time_start = time();
// 检查是否已经超时
function check_timeout(){
    // 开始时间
    global $time_start;
    // 5秒超时
    $timeout = 5;
    if(time()-$time_start > $timeout){
        exit("超时{$timeout}秒\n");
    }
}
// Zend引擎每执行一次低级语句就执行一下check_timeout
register_tick_function(&#39;check_timeout&#39;);
// 模拟一段耗时的业务逻辑
while(1){
   $num = 1;
}
// 模拟一段耗时的业务逻辑，虽然是死循环，但是执行时间不会超过$timeout=5秒
while(1){
   $num = 1;
}

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2. declare(ticks=1); Each time a low-level statement is executed, the process will be checked to see if there are unhandled signals. The test code is as follows:
Run php signal.php Then CTL+c or kill -SIGINT PID will cause the running code to jump out of the infinite loop to run the function registered by pcntl_signal. The effect is that the script exit prints "Get signal SIGINT and exi" Exit

# ##

<?php
declare(ticks=1);
pcntl_signal(SIGINT, function(){
   exit("Get signal SIGINT and exit\n");
});
echo "Ctl + c or run cmd : kill -SIGINT " . posix_getpid(). "\n" ;
while(1){
  $num = 1;
}

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