php declare(ticks)

<?php
// A function that records the time when it is called
function profile($dump = FALSE)
{
    static $profile;

    // Return the times stored in profile, then erase it
    if ($dump) {
        $temp = $profile;
        unset($profile);
        return ($temp);
    }

    $profile[] = microtime();
}

// Set up a tick handler
register_tick_function("profile");

// Initialize the function before the declare block
profile();

// Run a block of code, throw a tick every 2nd statement
/**
 *
 * decalre 体中  没执行ticks条低级语句就会执行一次callback
 * 如下例
 *for循环整个算一个低级语句  echo 算一个低级语句
 * 也就是说 一个for循环执行完 算2次 那么
 * ticks=4 就是执行2个for循环后 会调用一次callback
 * 所以最后数组中会有25个元素
 */
declare(ticks=4) {
for ($x = 1; $x < 50; ++$x) {
   // echo similar_text(md5($x), md5($x*$x)), "<br />;";
    echo $x.'<br/>';
}
}

// Display the data stored in the profiler
print_r(profile (TRUE));
?>