PHP microtime vs time for Performance Tracking

Measuring execution speed is crucial for optimizing PHP applications, and developers often choose between the microtime() and time() functions. While both functions retrieve the current system time, they differ significantly in precision, return formats, and suitability for benchmarking. This article explains the key differences between microtime() and time(), demonstrating why microtime() is the necessary choice for accurate performance tracking and how to implement it.

The Key Difference: Precision

The fundamental difference between time() and microtime() is the level of precision they offer:

• time() returns the current Unix timestamp as an integer, which measures time in seconds.
• microtime() returns the current Unix timestamp with microseconds (millionths of a second).

Because modern PHP scripts and database queries execute in a fraction of a second, the one-second resolution of time() is too coarse for performance tracking.

Why time() Fails for Performance Tracking

If you attempt to measure the execution time of a PHP function using time(), the result will almost always be inaccurate.

$start = time();
// Run a fast database query or loop
$end = time();
$executionTime = $end - $start;

In most cases, $executionTime will register as 0 because the code executed in less than a second. If the execution happens to span across the boundary of a second (e.g., starting at 12:00:00.99 and ending at 12:00:01.01), time() will report an execution time of 1 second, even though the actual duration was only 0.02 seconds.

Why microtime() is the Correct Choice

To accurately benchmark PHP code, you need microsecond precision. By default, microtime() returns a string in the format “msec sec” (e.g., “0.012345 1600000000”).

To make calculations easy, you should pass true as the first argument: microtime(true). This instructs PHP to return the timestamp as a float, representing the total number of seconds since the Unix epoch, inclusive of microseconds.

Here is the standard way to measure execution time using microtime():

$start = microtime(true);

// Code block to measure
usleep(50000); // Simulating a 50-millisecond delay

$end = microtime(true);
$executionTime = $end - $start;

echo "Execution time: " . round($executionTime, 4) . " seconds";

In this setup, if the code takes 50 milliseconds to execute, microtime(true) will accurately calculate and display 0.05 seconds.

Summary of Differences