Customizing Xdebug Profiler Output Filename and Analyzing PHP Performance on macOS

When Xdebug is enabled, the profiler creates output files (typically named cachegrind.out.xxxx ) that can be analyzed with third‑party tools. If you work on multiple projects, having all profiles in a single file becomes inconvenient.

You can customize the output filename by setting the xdebug.profiler_output_name directive in php.ini . The directive supports several placeholders:

Symbol

Meaning

Example Pattern

Resulting Filename

%c

CRC32 of the current working directory

cachegrind.out.%c

cachegrind.out.1258863198

%p

Current process ID

cachegrind.out.%p

cachegrind.out.9685

%r

Random number

cachegrind.out.%r

cachegrind.out.072db0

%s

Script filename

cachegrind.out.%s

cachegrind.out._home_httpd_html_test_xdebug_test_php

%t

Unix timestamp (seconds)

cachegrind.out.%t

cachegrind.out.1179434742

%u

Unix timestamp (microseconds)

cachegrind.out.%u

cachegrind.out.1179434749_642382

%H

$_SERVER["HTTP_HOST"]

cachegrind.out.%H

cachegrind.out.localhost

%R

$_SERVER["REQUEST_URI"]

cachegrind.out.%R

cachegrind.out._test_xdebug_test_php_var=1_var2

%S

Session ID (from $_COOKIE if set)

cachegrind.out.%S

cachegrind.out.c70c1ec2375af58f74b390bbdd2a679d

%%

Literal % character

cachegrind.out.%%

cachegrind.out.%%

Edit php.ini and add a line such as:

<code>xdebug.profiler_output_name = cachegrind.out.%H</code>

After saving the file, restart your PHP server.

On macOS, the profile files are stored in the /var/tmp/ directory.

For performance analysis, you can use MacCallGrind (paid) or the free qcachegrind . Both require Graphviz for call‑graph visualization.

Install the required tools with Homebrew:

<code>$ brew install graphviz</code>

<code>$ brew install qcachegrind</code>

Once installed, launch qcachegrind and open a cachegrind.out.* file to view the graphical analysis.

Be aware that enabling profiling can quickly fill disk space if many projects generate files. You can clean up old profiles with:

<code>$ sudo rm -fr /private/var/tmp/cachegrind.out.*</code>

Regular cleanup helps prevent excessive disk usage.