Page 520 - Beginning PHP 5.3

Part III: Using PHP in Practice
Note that using echo() only displays the number of seconds to two decimal places. To see the floating -
point number more precisely, you can use printf() :
// Displays, for example, “1230613358.459682”
printf( “%0.6f”, microtime( true ) );

One common scenario where microseconds are useful is when benchmarking your code to find speed
bottlenecks. By reading the microtime() value before and after performing an operation, and then
subtracting one value from the other, you can find out how long the operation took to execute. Here ’ s an
example:

< !DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.0 Strict//EN”
“http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd” >
< html xmlns=”http://www.w3.org/1999/xhtml” xml:lang=”en” lang=”en” >
< head >
< title > Timing script execution < /title >
< link rel=”stylesheet” type=”text/css” href=”common.css” / >
< /head >
< body >

< h1 > Timing script execution < /h1 >
< ?php

// Start timing
$startTime = microtime( true );

// Perform the operation
for ( $i=0; $i < 10; $i++ ) {
echo “ < p > Hello, world! < /p > ”;
}

// Stop timing
$endTime = microtime( true );
$elapsedTime = $endTime - $startTime;
printf( “ < p > The operation took %0.6f seconds to execute. < /p > ”, $elapsedTime );

? >
< /body >
< /html >
You can see a sample output from this script in Figure 16 - 1.

482

9/21/09 9:15:31 AM
c16.indd 482 9/21/09 9:15:31 AM
c16.indd 482