Detailed explanation of the declare command and usage of php

definition

The declare structure in php is used to set the execution instructions of a piece of code.

Declare is used to execute 3 instructions: ticks, encoding, strict_types

Scope

Declare structure is used for global scope, affecting all subsequent codes
(But if a file with declare structure is included by other files, it will not work for the parent file containing it)

declare(ticks=1) {
//Code
}
||
declare(ticks=1);
The two are equal

//effect://The time when the interpreter will happen every time N timeable low-level statements are executed by the interpreter declare(directive=N) Tick(clock cycle)//1. Every time a statement is executed, the registered function registered by register_tisk_function() is executed once.declare(ticks=1);
$time_start = time();
echo "hello";
function check_timeout(){
    global $time_start;
    $timeout=5;
    if (time() - $time_start > $timeout){
        exit("time out{$timeout}Second\n");
    }
}
register_tick_function('check_timeout');
$i=0;
while (1){
//    echo $i++;
    $num =1;
}
//2. Every time the low-level statement is executed, the process will be checked for unprocessed signals.pcntl_signal(SIGINT,function (){
    exit("Get signal SIGINT and exit\n");
});
echo "Ctrl+C or run cmd:kill -SIGINT".posix_getpid()."\n";
while (1){
//    echo "hello world";
    $num = 1;
}

You can use the encoding directive to specify how each script is encoded.

declare(encoding='cp936');  //Must be on the first line of the file code

3.strict_types

Turn on strict mode. The default is weak type verification.

declare(strict_types=1);

The following content is reproduced from:/kudosharry/p/

Usage of declare in php

function tick_handler ()		
{			
echo  "tick_handler() called<br>" ;		
}		 
function  tick_handler1 ()		
{			
echo  "tick_handler1() called<br>" ;		
}
 register_tick_function ( 'tick_handler' );		
 register_tick_function ( 'tick_handler1' );
declare( ticks = 1 )
{			 
$a  =  1 ;
			
if ( $a  >  0 ) 
{				
 $a  +=  2 ;				
print( $a );			
}		
}		
exit;

Here, two functions are defined first, and then registered to the system. Then, a ticks is defined through declare, with a step size of 1. The function is that every time the code in the declare scope executes the ticks step size, the registration method is executed once, and the method is in line with the order of registration.

So the above execution result is:

tick_handler() called
tick_handler1() called
tick_handler() called
tick_handler1() called
3tick_handler() called
tick_handler1() called
tick_handler() called
tick_handler1() called
tick_handler() called
tick_handler1() called
tick_handler() called
tick_handler1() called

This method can test the processing time of executing the code.

The above is the detailed explanation of the php declare command and usage. For more information about the usage of php declare, please follow my other related articles!