Pro PHP- Patterns, Frameworks, Testing and More

CHAPTER 8 ■ TESTING, DEPLOYMENT, AND CONTINUOUS INTEGRATION^123

Profiling with Xdebug.

You can use the following functions to get profile information:

int xdebug_memory_usage(): This function returns the current memory usage at the time

the function is called.

int xdebug_peak_memory_usage(): This function returns the greatest amount of memory

the script has used from script startup until the time the function is called.

float xdebug_time_index(): This function returns the time in seconds since the script

began running. It’s very precise and will allow you to track down slow sections of code.

Xdebug also ships with an application-wide profiler that saves information about which

functions were called during execution and how many times each was called. To enable this

profiler, add the following to your php.ini file:

xdebug.profiler_enable=1

xdebug.profiler_output_dir=/path/you/want/profile/file/placed

This enables the profiler to start saving information. To read the information, you will

need an analyzer like KCacheGrind or WinCacheGrind.

■Caution Use the application-wide profiler feature only when necessary, as it will add significant overhead

to your PHP scripts. Additionally, the profile files can use up significant amounts of disk space.

Checking Code Coverage with Xdebug

It is often useful to know how effective your library organization is. Theoretically, if only a fraction

of the code in a given file is commonly executed, you may get some performance gain by

breaking up the file into two or more files. However, as with all performance optimization, it is

important not to get carried away. Code coverage can also help you identify if code never gets

called and is simply dead or inaccessible.

The code-coverage functionality provided by Xdebug comes in the form of a function that

tells you exactly which lines of a file have been run during any given execution, as well as functions

to pause and get code coverage:

void xdebug_start_code_coverage( [int options] ): This function begins collecting

code-coverage information. It has two options: XDEBUG_CC_UNUSED and XDEBUG_CC_DEAD_

CODE, both of which can be used to determine if code is callable.

void xdebug_stop_code_coverage( ): This function pauses the collection of code-coverage

data.

array xdebug_get_code_coverage( ): This function returns a multidimensional array, where

the format is $array[filename][line] = numberofcalls;

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