switch
The scope of the declare() call if used without a block is a little unpredictable, in my experience. It appears that if placed in a method or function, it may not apply to the calls that ensue, like the following:
<?php
function a()
{
declare(ticks=2);
b();
}
function b()
{
// The declare may not apply here, sometimes.
}
?>
So, if all of a sudden the signals are getting ignored, check this. At the risk of losing the ability to make a mathematical science out of placing a number of activities at varying durations of ticks like many people have chosen to do, I've found it simple to just put this at the top of the code, and just make it global.
declare
(PHP 4, PHP 5)
El constructor declare es usado para fijar directivas de ejecución para un bloque de código. La sintaxis de declare es similar a la sintaxis de otros constructores de control de flujo:
declare (directive)
statement
La sección directive permite que el comportamiento de declare sea configurado. Actualmente, sólo dos directivas están reconocidas: ticks (Ver abajo para más información sobre la directiva ticks) y encoding (Ver abajo para más información sobre la directiva encoding ).
Nota: La directiva encoding fue agregada en PHP 5.3.0
La parte statement del bloque declare será ejecutada - como se ejecuta y que efectos secundarios ocurran durante la ejecución puede depender de la directiva fijada en el bloque directive.
El constructor declare también se puede utilizar en el alcance global, afectando a todo el código que le sigue (sin embargo, si el archivo con el declare fue incluido entonces no afectará al archivo padre).
<?php
// estos son lo mismo:
// se puede usar ésto:
declare(ticks=1) {
// script entero aquí
}
// o se puede usar ésto:
declare(ticks=1);
// script entero aquí
?>
Ticks
Un tick es un evento que ocurre para cada
sentencia tickable N de bajo nivel ejecutada
por el intérprete dentro del bloque declare.
El valor para N se especifica
usando ticks=N
dentro del bloque de declare
de la sección directive.
No todas las sentencias son tickable. Por lo general, expresiones de condición y expresiones de argumento no son tickables.
Los eventos que ocurren en cada tick se especifican mediante la register_tick_function(). Ver el ejemplo abajo para más detalles. Tener en cuenta que más de un evento puede ocurrir por cada tick.
Ejemplo #1 Ejemplo de uso del tick
<?php
declare(ticks=1);
// Una función llamada en cada evento tick
function tick_handler()
{
echo "tick_handler() llamado\n";
}
register_tick_function('tick_handler');
$a = 1;
if ($a > 0) {
$a += 2;
print($a);
}
?>
Ejemplo #2 Ejemplo de uso de ticks
<?php
function tick_handler()
{
echo "tick_handler() llamado\n";
}
$a = 1;
tick_handler();
if ($a > 0) {
$a += 2;
tick_handler();
print($a);
tick_handler();
}
tick_handler();
?>
Véase también register_tick_function() y unregister_tick_function().
Encoding
Una codificación de script puede ser especificada para cada script usando la directiva encoding.
Ejemplo #3 Declarando un encoding para el script
<?php
declare(encoding='ISO-8859-1');
// código aquí
?>
Precaución
Cuando se combina con espacios de nombres, la única sintaxis legal para declarar es declare(encoding='...'); donde ... es el valor del encoding. declare(encoding='...') {} resultará en un error de análisis cuando se combina con espacios de nombres.
El valor declarado de encoding es ignorado en PHP 5.3 a menos que php esté compilado con --enable-zend-multibyte.
Tener en cuenta que PHP no expone si --enable-zend-multibyte fue utilizado para compilar PHP que no sea por phpinfo().
Ver también zend.script_encoding.
add a note
User Contributed Notes
declare - [17 notes]
aeolianmeson at NOSPAM dot blitzeclipse dot com ¶
7 years ago
fok at nho dot com dot br ¶
9 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. =--
Kamil Pawelkiewicz ¶
8 months ago
I've created memory usage monitor class using tick event.
The result is returned in a fancy graph using GD library.
You can get the source, readme and example script at:
https://github.com/kampaw/profiler
Usage is very simple:
<?php
require('profiler.php');
$profiler = new profiler;
declare(ticks = 1000);
// monitor started
// insert your code here
$profiler->chart();
?>
Anonymous ¶
2 years ago
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.
ramamneh at gmail dot com ¶
2 years ago
check loaded server connection
<?php
$connection = false;
function checkConnection( $connectionWaitingTime = 3 )
{
// check connection & time
global $time,$connection;
if( ($t = (time() - $time)) >= $waitingTime && !$connection){
echo ("<p> Server not responding for <strong>$t</strong> seconds !! </p>");
die("Connection aborted");
}
}
register_tick_function("checkConnection");
$time = time();
declare (ticks=1)
{
while( true ){ // connecting to loaded server
}
$connection = true ;
}
?>
markandrewslade at dontspamemeat dot gmail ¶
4 years ago
Note that the two methods for calling declare are not identical.
Method 1:
<?php
// Print "tick" with a timestamp and optional suffix.
function do_tick($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.
anotheruser at example dot com ¶
4 years ago
Code evaluation script which uses debug_backtrace() to get execution time in ns, relative current line number, function, file, and calling function info on each tick, and shove it all in $script_stats array. See debug_backtrace manual to customize what info is collected.
Warning: this will exhaust allowed memory very easily, so adjust tick counter according to the size of your code. Also, array_key_exists checking on debug_backtrace arrays is removed here only to keep this example simple, but should be added to avoid a large number of resulting PHP Notice errors.
<?php
$script_stats = array();
$time = microtime(true);
function track_stats(){
global $script_stats,$time;
$trace = debug_backtrace();
$exe_time = (microtime(true) - $time) * 1000;
$func_args = implode(", ",$trace[1]["args"]);
$script_stats[] = array(
"current_time" => microtime(true),
"memory" => memory_get_usage(true),
"file" => $trace[1]["file"].': '.$trace[1]["line"],
"function" => $trace[1]["function"].'('.$func_args.')',
"called_by" => $trace[2]["function"].' in '.$trace[2]["file"].': '.$trace[2]["line"],
"ns" => $exe_time
);
$time = microtime(true);
}
declare(ticks = 1);
register_tick_function("track_stats");
// the rest of your project code
// output $script_stats into a html table or something
?>
rosen_ivanov at abv dot bg ¶
6 years ago
As Chris already noted, ticks doesn't make your script multi-threaded, but they are still great. I use them mainly for profiling - for example, placing the following at the very beginning of the script allows you to monitor its memory usage:
<?php
function profiler($return=false) {
static $m=0;
if ($return) return "$m bytes";
if (($mem=memory_get_usage())>$m) $m = $mem;
}
register_tick_function('profiler');
declare(ticks=1);
/*
Your code here
*/
echo profiler(true);
?>
This approach is more accurate than calling memory_get_usage only in the end of the script. It has some performance overhead though :)
xxoes ¶
10 years ago
If i use ticks i must declare all functions before i call the function.
example:
Dosn't work
<?php
function ticks() {
echo "tick";
}
register_tick_function("ticks");
declare (ticks=1) 1;
echo "";
echo "";
foo(); // Call to undefined function.
function foo() {
echo "foo";
}
?>
Work
<?php
function ticks() {
echo "tick";
}
register_tick_function("ticks");
//declare (ticks=1) 1;
echo "";
echo "";
foo();
function foo() {
echo "foo";
}
?>
win2k : PHP 4.3.0 (cgi-fcgi)
warhog at warhog dot net ¶
7 years ago
as i read about ticks the first time i thought "wtf, useless crap" - but then i discovered some usefull application...
you can declare a tick-function which checks each n executions of your script whether the connection is still alive or not, very usefull for some kind of scripts to decrease serverload
<?php
function check_connection()
{ if (connection_aborted())
{ // do something here, e.g. close database connections
// (or use a shutdown function for this
exit; }
}
register_tick_function("connection");
declare (ticks=20)
{
// put your PHP-Script here
// you may increase/decrease the number of ticks
}
?>
chris-at-free-source.com ¶
8 years ago
Also note that PHP is run in a single thread and so everything it does will be one line of code at a time. I'm not aware of any true threading support in PHP, the closest you can get is to fork.
so, declare tick doens't "multi-thread" at all, it is simply is a way to automaticaly call a function every n-lines of code.
daniel@swn ¶
10 years ago
<?php
ob_end_clean();
ob_implicit_flush(1);
function a() {
for($i=0;$i<=100000;$i++) { }
echo "function a() ";
}
function b() {
for($i=0;$i<=100000;$i++) { }
echo "function b() ";
}
register_tick_function ("a");
register_tick_function ("b");
declare (ticks=4)
{
while(true)
{
sleep(1);
echo "\n<br><b>".time()."</b><br>\n";;
}
}
?>
You will see that a() and b() are slowing down this process. They are in fact not executed every second as expected. So this function is not a real alternative for multithreading using some slow functions..there is no difference to this way: while (true) { a(); b(); sleep(1); }
rob_spamsux at rauchmedien dot ihatespam dot com ¶
11 years ago
Correction to above note:
Apparently, the end brace '}' at the end of the statement causes a tick.
So using
------------
declare (ticks=1) echo "1 tick after this prints";
------------
gives the expected behavior of causing 1 tick.
Note: the tick is issued after the statement executes.
Also, after playing around with this, I found that it is not really the multi-tasking I had expected. It behaves the same as simply calling the functions. I.e. each function must finish before passing the baton to the next function. They do not run in parallel.
It also seems that they always run in the order in which they were registered.
So,
<?php
------------
# register tick functions
register_tick_function ("a");
register_tick_function ("b");
# make the tick functions run
declare (ticks=1);
?>
------------
is equivalent to
------------
a();
b();
------------
It is simply a convenient way to have functions called periodically while some other code is being executed. I.e. you could use it to periodically check the status of something and then exit the script or do something else based on the status.
Tom Samplonius ¶
2 years ago
The tick handler is intended for code profiling. You can use it to determine the number of time units (ticks) that a chunk of code takes. And you can vary the tick frequency so profiling doesn't impact your specific code too much. A tick handler can gather other useful performance data, besides just counting ticks.
You can use the tick handler to poll that your connection is a alive, but this will block your entire script. Polling connection status is no substitute for checking return values, and using timeouts on any function that connects to an external system.
rob_spamsux at rauchmedien dot ihatespam dot com ¶
11 years ago
Here is an example of multi-tasking / multi-threading:
<?php
# declare functions
function a() {
echo "a";
}
function b() {
echo "b";
}
# register tick functions
register_tick_function ("a");
register_tick_function ("b");
# make the tick functions run
declare (ticks=1);
# that's all there is to it.
?>
Notes:
This will make functions a and b run once each at the same time.
If you try:
declare (ticks=1) {
1;
}
They will run twice each. That is because it seems to be an undocumented fact that there is always an extra tick.
Therefore:
declare (ticks=2) {
1;
}
Will cause them to run once.
zabmilenko at charter dot net ¶
5 years ago
If you misspell the directive, you won't get any error or warning. The declare block will simply act as a nest for statements:
<?php
declare(tocks="four hundred")
{
// Has no affect on code and produces
// no error or warning.
}
?>
Tested in php 5.2.5 on XPsp2
rsemil at gmail dot com ¶
5 years ago
rosen_ivanov's solution can be replaced by a simple call to memory_get_peak_usage() if you're running at least PHP 5.2.0