declare (original) (raw)

(PHP 4, PHP 5, PHP 7)

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

declare (directive) statement

The directive section allows the behavior of the declare block to be set. Currently only three directives are recognized: theticks directive (See below for more information on theticks directive), the encoding directive (See below for more information on theencoding directive) and the strict_types directive (See for more information thestrict section on the Function arguments page)

As directives are handled as the file is being compiled, only literals may be given as directive values. Variables and constants cannot be used. To illustrate:

<?php // This is valid: declare(ticks=1);// This is invalid: const TICK_VALUE = 1; declare(ticks=TICK_VALUE); ?>

The statement part of thedeclare block will be executed - how it is executed and what side effects occur during execution may depend on the directive set in thedirective block.

The declare construct can also be used in the global scope, affecting all code following it (however if the file withdeclare was included then it does not affect the parent file).

`<?php
// these are the same:

// you can use this:

declare(ticks=1) {
// entire script here
}// or you can use this:
declare(ticks=1);
// entire script here
?> `

Ticks

A tick is an event that occurs for everyN low-level tickable statements executed by the parser within the declare block. The value for N is specified using ticks=N within the declare block'sdirective section.

Not all statements are tickable. Typically, condition expressions and argument expressions are not tickable.

The event(s) that occur on each tick are specified using theregister_tick_function(). See the example below for more details. Note that more than one event can occur for each tick.

Example #1 Tick usage example

`<?phpdeclare(ticks=1);// A function called on each tick event
function tick_handler()
{
echo "tick_handler() called\n";
}register_tick_function('tick_handler');$a = 1;

if (

$a > 0) {
$a += 2;
print($a);
}?> `

Example #2 Ticks usage example

`<?phpfunction tick_handler()
{
echo "tick_handler() called\n";
}$a = 1;
tick_handler();

if (

$a > 0) {
$a += 2;
tick_handler();
print($a);
tick_handler();
}
tick_handler();?> `

See also register_tick_function() andunregister_tick_function().

Encoding

A script's encoding can be specified per-script using the encoding directive.

Example #3 Declaring an encoding for the script.

<?php declare(encoding='ISO-8859-1'); // code here ?>

Caution

When combined with namespaces, the only legal syntax for declare is declare(encoding='...'); where ... is the encoding value. declare(encoding='...') {} will result in a parse error when combined with namespaces.

The encoding declare value is ignored in PHP 5.3 unless php is compiled with--enable-zend-multibyte.

Note that PHP does not expose whether --enable-zend-multibyte was used to compile PHP other than by phpinfo().

See also zend.script_encoding.