English
English
In PHP, time_nanosleep is a function for precise control of delays, which allows developers to pause program execution in seconds and nanoseconds. It provides higher temporal resolution than sleep or usleep . However, developers often encounter problems that it "does not seem to work" when using time_nanosleep . This article will discuss possible reasons and debugging methods.
<?php
echo "start...\n";
time_nanosleep(0, 500000000); // pause0.5Second
echo "Finish...\n";
?>
In this example, the program should pause for 0.5 seconds after outputting "Start..." and then output "End...".
If you try to use very short delays (such as 100 milliseconds or less), it is difficult to detect the delay effect from the terminal or browser output. For example:
time_nanosleep(0, 100000); // 0.1毫Second
The delay is very short at this time, and unless you count the execution time in a loop or performance-sensitive environment, the delay is almost impossible to detect.
If you use time_nanosleep in a web page, the browser will not immediately display the intermediate output on the server side. That is, even if you pause for 0.5 seconds on the server side, the browser may not display the content until the entire page has finished rendering.
The solution is to use a buffer control function, for example:
ob_flush();
flush();
time_nanosleep(0, 500000000);
echo "Continue to execute";
However, it should be noted that the output buffer settings of the web server (such as Nginx or Apache) themselves will also affect the effect.
Not all operating systems and PHP compilation environments can support latency precise to nanoseconds. On some platforms, time_nanosleep may be degraded to an approximate implementation, where the actual delay may be biased from the expected value. You can use hrtime(true) to verify the actual delay:
$start = hrtime(true);
time_nanosleep(0, 500000000);
$end = hrtime(true);
echo "Delay time: " . ($end - $start) / 1e6 . " 毫Second";
If the output is much larger than 500 milliseconds, it may mean that the system level does not support accurate delay.
If your PHP script is interrupted during runtime (such as user abort, timeout setting, blunt exit() ), time_nanosleep may not have a chance to complete execution. You can test by setting ignore_user_abort(true) ;:
ignore_user_abort(true);
time_nanosleep(1, 0);
hrtime() provides a nanosecond-level timestamp, which is ideal for verifying that delays are in effect.
The output in the command line environment is real-time, making it easier to observe the behavior of time_nanosleep .
php test_sleep.php
Insert logging points in the program:
file_put_contents('/var/log/sleep.log', date('H:i:s') . " before\n", FILE_APPEND);
time_nanosleep(0, 500000000);
file_put_contents('/var/log/sleep.log', date('H:i:s') . " after\n", FILE_APPEND);
Observing the time difference between the two logs can effectively determine whether the delay is effective.
If you use time_nanosleep in a high frequency loop, you can use the top or htop tool to see if the CPU usage has decreased to determine whether the pause has actually occurred.
Suppose you are sending multiple requests to https://gitbox.net/api/ping , and you need to pause for 0.25 seconds between each request:
for ($i = 0; $i < 5; $i++) {
file_get_contents("https://gitbox.net/api/ping");
echo "1. $i The request was sent completed\n";
time_nanosleep(0, 250000000); // 250毫Second
}
Combining CLI and hrtime() , you can more accurately verify the delay effect.
time_nanosleep is a practical but misunderstood delay function in PHP. It is not invalid, it is simply limited by platform support, execution environment and output buffering mechanism. Understanding these differences and combining debugging techniques can effectively use time_nanosleep to achieve more accurate delay control.
