It's amazing how many people didn't grasp the concept here. Note the wording in the documentation. It states that the tick handler is called every n native execution cycles. That means native instructions, not including system calls (i'm guessing). This can give you a very good idea if you need to optimize a particular part of your script, since you can measure quite effectively how many native instructions are in your actual code.
A good profiler would take that into account, and force you, the developer, to include calls to the profiler as you're entering and leaving every function. That way you'd be able to keep an eye on how many cycles it took each function to complete. Independent of time.
That is extremely powerful, and not to be underestimated. A good solution would allow aggregate stats, so the total time in a function would be counted, including inside called functions.
declare
(PHP 4, PHP 5, PHP 7, PHP 8)
Das declare-Konstrukt wird verwendet, um
Ausführungsdirektiven für einen Codeblock festzulegen. Die Syntax von
declare ist ähnlich wie die Syntax anderer
Ablauf-Kontrollstrukturen:
declare (directive)
statement
Die directive-Sektion erlaubt es, das Verhalten des
declare-Blocks anzugeben.
Aktuell werden nur drei Direktiven unterstützt: die
ticks-Direktive (siehe unten für weitere Informationen über
die ticks-Direktive),
die encoding-Direktive (siehe unten für weitere
Informationen über die encoding-Direktive),
und die strict_types-Direktive (siehe den Abschnitt über
strict typing
auf der Seite über Typendeklarationen).
Da Direktiven behandelt werden, wenn die Datei kompiliert wird, dürfen nur Literale als Direktiven-Werte angegeben werden. Variable und Konstante können nicht verwendet werden. Zur Veranschaulichung:
<?php
// Dies ist erlaubt:
declare(ticks=1);
// Dies ist ungültig:
const TICK_VALUE = 1;
declare(ticks=TICK_VALUE);
?>
Der statement-Teil des declare-Blocks
wird ausgeführt - wie genau die Ausführung aussieht und welche Seiteneffekte
während der Ausführung auftreten können, ist abhängig von der im
directive-Block gesetzten Direktive.
Das declare-Konstrukt kann außerdem im globalen
Sichtbarkeitsbereich verwendet werden, es hat dann Auswirkungen auf den
gesamten folgenden Code (wird die Datei mit der
declare-Anweisung inkludiert, hat die Anweisung jedoch
keine Auswirkung auf das einbindende File).
<?php
// dies sind gleichwertige Schreibweisen:
// Sie können diese Schreibweise verwenden:
declare(ticks=1) {
// hier das vollständige Skript einfügen
}
// oder diese:
declare(ticks=1);
// hier das vollständige Skript einfügen
?>Ticks
Ein Tick ist ein Event, das für alle N Low-Level-Statements
auftritt, die vom Parser innerhalb des declare-Blocks
ausgeführt werden.
Der Wert für N wird durch die Verwendung von
ticks=N innerhalb der
directive-Sektion des declare-Blocks
angegeben.
Nicht alle Statements führen zu einem Tick-Event. So etwa Konditionen und Argumente.
Das/die bei jedem Tick auftretenden Event(s) werden durch die Verwendung der Funktion register_tick_function() angegeben. Betrachten Sie das folgende Beispiel für mehr Details. Beachten Sie, dass mehr als ein Event bei jedem Tick auftreten kann.
Beispiel #1 Tick Nutzungsbeispiel
<?php
declare(ticks=1);
// Funktion, welche bei jeden Tick-Event aufgerufen wird
function tick_handler()
{
echo "tick_handler() aufgerufen\n";
}
register_tick_function('tick_handler'); // löst ein Tick-Ereignis aus
$a = 1; // löst ein Tick-Ereignis aus
if ($a > 0) {
$a += 2; // löst ein Tick-Ereignis aus
print $a; // löst ein Tick-Ereignis aus
}
?>Siehe auch register_tick_function() und unregister_tick_function().
Encoding
Das Encoding eines Skripts kann pro Skript mittels der encoding-Direktive
festgelegt werden.
Beispiel #2 Das Encoding eines Skripts deklarieren.
<?php
declare(encoding='ISO-8859-1');
// hier folgt der Code
?>Achtung
Die einzig zulässige Syntax für ein declare, das mit Namespaces kombiniert
wird, ist declare(encoding='...');, wobei
... der Name des Encodings ist.
declare(encoding='...') {} führt zu einem Parse-Error,
wenn es mit Namespaces kombiniert wird.
Siehe auch zend.script_encoding.
add a note
User Contributed Notes 10 notes
Anonymous ¶
14 years ago
Kubo2 ¶
9 years ago
Note that in PHP 7 <?php declare(encoding='...'); ?> throws an E_WARNING if Zend Multibyte is turned off.
digitalaudiorock at gmail dot com ¶
5 years ago
A few important things to note for anyone using this in conjunction with signal handlers:
If anyone is trying to optionally use either pcntl_async_signals() when available (PHP >= 7.1) or ticks for older versions, this is not possible...at least not in a way that does NOT enable ticks for newer PHP versions. This is because there is simply no way to conditionally declare ticks. For example, the following will "work" but not in the way you might expect:
<?php
if (function_exists('pcntl_async_signals')) {
pcntl_async_signals(true);
} else {
declare(ticks=1);
}
?>
While signal handlers will work with this for old and new version, ticks WILL be enabled even in the case where pcntl_async_signals exists, simply because the declare statement exists. So the above is functionally equivalent to:
<?php
if (function_exists('pcntl_async_signals')) pcntl_async_signals(true);
declare(ticks=1);
?>
Another thing to be aware of is that the scoping of this declaration changed a bit from PHP 5.6 to 7.x...actually it was corrected apparently as noted here:
http://php.net/manual/en/function.register-tick-function.php#121204
This can cause some very confusing behavior. One example is with the pear/System_Daemon module. With PHP 5.6 that will work with a SIGTERM handler even if the script using it doesn't itself use declare(ticks=1), but does not work in PHP 7 unless the script itself has the declaration. Not only does the handler not get called, but the signal does nothing at all, and the script doesn't exit.
A side note regarding ticks that's annoyed me for some time: As if there wasn't enough confusion around all this, the Internet is full of false rumors that ticks were deprecated and are being removed, and I believe they all started here:
http://www.hackingwithphp.com/4/21/0/the-declare-function-and-ticks
Despite a very obscure author's note at the very end of the page saying he got that wrong (that even I just noticed), the first very prominent sentence of the article still says this, and that page is near the top of any Google search.
sawyerrken at gmail dot com ¶
11 years ago
In the following example:
<?php
function handler(){
print "hello <br />";
}
register_tick_function("handler");
declare(ticks = 1){
$b = 2;
} //closing curly bracket tickable
?>
"Hello" will be displayed twice because the closing curly bracket is also tickable.
One may wonder why the opening curly bracket is not tickable if the closing is tickable. This is because the instruction for PHP to start ticking is given by the opening curly bracket so the ticking starts immediately after it.
digitalaudiorock at gmail dot com ¶
5 years ago
Regarding my previous comment as to the change in scope of declare(ticks=1) between 5.6 and 7.x, I intended to mention another example of the affect this can have on signal handlers:
If your script uses declare(ticks=1) and assigns handlers, in 5.6 signals will get caught and call the handler even when the code that is running is in an included file (where the included file doesn't have the declaration). However in 7.x the signal wouldn't get caught until the code returns to the main script.
The best solution to that is to use pcntl_async_signals(true) when it's available, which will allow the signals to get caught regardless of what file the code happens to be in.
php dot net at e-z dot name ¶
11 years ago
you can register multiple tick functions:
<?PHP
function a() { echo "a\n"; }
function b() { echo "b\n"; }
register_tick_function('a');
register_tick_function('b');
register_tick_function('b');
register_tick_function('b');
?>
will output on every tick:
a
b
b
b
fok at nho dot com dot br ¶
21 years ago
This is a very simple example using ticks to execute a external script to show rx/tx data from the server
<?php
function traf(){
passthru( './traf.sh' );
echo "<br />\n";
flush(); // keeps it flowing to the browser...
sleep( 1 );
}
register_tick_function( "traf" );
declare( ticks=1 ){
while( true ){} // to keep it running...
}
?>
contents of traf.sh:
# Shows TX/RX for eth0 over 1sec
#!/bin/bash
TX1=`cat /proc/net/dev | grep "eth0" | cut -d: -f2 | awk '{print $9}'`
RX1=`cat /proc/net/dev | grep "eth0" | cut -d: -f2 | awk '{print $1}'`
sleep 1
TX2=`cat /proc/net/dev | grep "eth0" | cut -d: -f2 | awk '{print $9}'`
RX2=`cat /proc/net/dev | grep "eth0" | cut -d: -f2 | awk '{print $1}'`
echo -e "TX: $[ $TX2 - $TX1 ] bytes/s \t RX: $[ $RX2 - $RX1 ] bytes/s"
#--= the end. =--
ja2016 at wir dot pl ¶
7 years ago
Don't use uft-8 encoding with BOM. Then fatal error occurs ALWAYS. Substitute it with utf-8 without BOM.
---
*BOM*
<?php
declare(strict_types=1);
//Fatal error: strict_types declaration must be the very first statement in the script
markandrewslade at dontspamemeat dot gmail ¶
15 years ago
Note that the two methods for calling declare are not identical.
Method 1:
<?php
// Print "tick" with a timestamp and optional suffix.
function do_tick($str = '') {
list($sec, $usec) = explode(' ', microtime());
printf("[%.4f] Tick.%s\n", $sec + $usec, $str);
}
register_tick_function('do_tick');
// Tick once before declaring so we have a point of reference.
do_tick('--start--');
// Method 1
declare(ticks=1);
while(1) sleep(1);
/* Output:
[1234544435.7160] Tick.--start--
[1234544435.7161] Tick.
[1234544435.7162] Tick.
[1234544436.7163] Tick.
[1234544437.7166] Tick.
*/
?>
Method 2:
<?php
// Print "tick" with a timestamp and optional suffix.
function do_tick($str = '') {
list($sec, $usec) = explode(' ', microtime());
printf("[%.4f] Tick.%s\n", $sec + $usec, $str);
}
register_tick_function('do_tick');
// Tick once before declaring so we have a point of reference.
do_tick('--start--');
// Method 2
declare(ticks=1) {
while(1) sleep(1);
}
/* Output:
[1234544471.6486] Tick.--start--
[1234544472.6489] Tick.
[1234544473.6490] Tick.
[1234544474.6492] Tick.
[1234544475.6493] Tick.
*/
?>
Notice that when using {} after declare, do_tick wasn't auto-called until about 1 second after we entered the declare {} block. However when not using the {}, do_tick was auto-called not once but twice immediately after calling declare();.
I'm assuming this is due to how PHP handles ticking internally. That is, declare() without the {} seems to trigger more low-level instructions which in turn fires tick a few times (if ticks=1) in the act of declaring.
ohcc at 163 dot com ¶
4 years ago
It's possible to set directives at one time if every directive is supported.
<?php
declare(strict_types=1, encoding='UTF-8');
?>
