


Use xdebug to analyze PHP programs and find performance bottlenecks
There is a famous 80-20 law in economics, which is quoted in programming: 80% of performance bottlenecks are caused by 20% of the code. With the help of PHP's XDebug extension, these 20% of code can be effectively found.
1. Installation and configuration
1. Download the XDebug extension for PHP at: http://xdebug.org/
2. Compile and install XDebug under Linux
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Note: /usr/local/php/lib/ php/extensions/no-debug-non-zts-20020429/Different PHP versions have different paths and do not have to be placed on this path. You can specify the location of xdebug.so in zend_extension_ts.
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Modify php.ini, remove the PHP acceleration module, and add the following configuration information to support XDebug extension
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3. Client (Windows): WinCacheGrind Download address: http://sourceforge.net/projects/wincachegrind/
II , Analysis process
1. Visit your website and click various links on the homepage several times. XDebug generates the following files in the /tmp/xdebug directory:
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2. Copy the above files to Windows and use client software WinCacheGrind opened each file and found that the following PHP program took the longest time to execute:
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3. Analysis results:
1, /usr/local/apache/htdocs/tag/tags.php
( 1) The longest time-consuming filter_tags function appears on line 158 of /usr/local/apache/htdocs/tag/tags.php:
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(2) The filter_tags function is quoted from /usr/local/apache/htdocs/include /misc.php, the getForbiddenTags function is called 21 times by the filter_tags function. Most of the time spent by the filter_tags function is caused by the getForbiddenTags function. The content of the getForbiddenTags function is as follows:
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(3) Analysis of the getForbiddenTags function shows that the PHP function trim was called 16827 times.
(4) Possible reasons for the bottleneck:
The 156 keywords to be filtered are stored line by line in the /usr/local/apache/template/tags/forbidden_tags.txt file, and the text database is not efficient .
The line-by-line reading function fgets and the function trim that removes blanks on both sides of a string or specified characters are inefficient under high load. You can test file reading functions such as fopen, fread, and fscanf for comparison.

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