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- PHP Manual
- Control Structures
- declare

## declare

(PHP 4, PHP 5, PHP 7, PHP 8)

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: the `ticks` directive (See below for more information on the ticks directive), the `encoding` directive (See below for more information on the encoding directive) and the `strict_types` directive (See for more information the strict typing section on the type declarations 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 the `declare` block will be executed - how it is executed and what side effects occur during execution may depend on the directive set in the `directive` block.

The `declare` construct can also be used in the global scope, affecting all code following it (however if the file with `declare` 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 every N 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's `directive` 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 the register_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 eventfunction tick_handler(){    echo "tick_handler() called\n";}register_tick_function('tick_handler'); // causes a tick event$a = 1; // causes a tick eventif ($a > 0) {    $a += 2; // causes a tick event    print $a; // causes a tick event}?>

See also register_tick_function() and unregister_tick_function().

### Encoding

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

Example #2 Declaring an encoding for the script.

    <?phpdeclare(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.

See also zend.script_encoding.