The declare declaration construct is used to set the execution directives for a block of code. The declare syntax is similar to the syntax of other PHP control constructs:

declare (директива)
инструкция;

The directive allows you to set the behavior of the declare block. Currently, only one directive is available in PHP - tick . The instruction is part of the declare block.

How the instruction (s) will be executed depends on the directive.

The declare construct can be used in a global scope, affecting all the code after it.

<?php
// Вы можете равнозначно использовать следующие методы

// Так:
declare(ticks=1) {
// Здесь полный сценарий
}

// Или так:
declare(ticks=1);
// Здесь полный сценарий
?>

Tick ​​directive

tick is an event that occurs for every lower-level N-instructions executed by the parser within the declare block. Events occurring on each tick are determined by the register_tick_function () function.

declare

The declare construct is used to set the execution directives for a block of code. The declare syntax is similar to the syntax of other flow control constructs:

  declare (directive) statement 

The directive section allows you to set the declare block behavior. Currently only one directive is recognized: ticks . (See further about the ticks directive.)

The statement part of the declare block will be executed — how it is executed and which side effects occur during execution depends on the directive set in the directive block.

Ticks / Tiki

A tick / tick is an event that occurs for each lower-level operator N performed by the parser inside the declare block. The value of N is specified by ticks = N inside the directive section of the declare block.

The event (s) that occurs with each tick is specified by the register_tick_function () function. See details further in the example. Note that more than one event may occur for each tick.

  <? php
 // A function that records the time when it is called
 function profile ($ dump = FALSE)
 {
     static $ profile;

     // Returns the time stored in the profile, then deleted
     if ($ dump) {
         $ temp = $ profile;
         unset ($ profile);
         return ($ temp);
     }

     $ profile [] = microtime ();
 }

 // Set the tick handler / tick handler
 register_tick_function ("profile");

 // Initialize the function before the declare block
 profile ();

 // The code block is executed, the tick is called on every second operator
 declare (ticks = 2) {
     for ($ x = 1; $ x <50; ++ $ x) {
         echo similar_text (md5 ($ x), md5 ($ x * $ x)), "<br />;";
     }
 }

 // Displays the data stored in the profiler
 print_r (profile (TRUE));
 ?> 

This example profiles the PHP code inside the 'declare' block, recording the time when each second low-level statement of the executed block is executed. This information can then be used to search for slow sections of a specific code segment. This process can be performed using other methods: the use of ticks is more convenient and easier to implement.

Ticks are well suited for debugging, implementing simple multitasking, background I / O, and many other tasks.

See also register_tick_function () and unregister_tick_function () .