How to debug memory leaks in PHP functions?

Debugging memory leaks in PHP functions is crucial, using tools such as xdebug, PHPUnit or Valgrind. The specific steps are as follows: 1. Use xdebug to add a tracking function and generate an .xdebug file containing leak information; 2. Use PHPUnit to create a test class with an assertion coverage of 100%; 3. Use Valgrind to run php and enable --leak-check= full option to view memory leak reports. With these tools, you can effectively identify and fix memory leaks, preventing performance issues and program crashes.

Debugging memory leaks in PHP functions

A memory leak means that the memory is no longer used by the program, but is still retained Case. This can cause performance issues or even program crashes. Debugging memory leaks in PHP is crucial and can help prevent these problems.

Tools

To debug memory leaks in PHP, you can use the following tools:

• xdebug
• PHPUnit
• Valgrind

Method

There are several ways to debug memory leaks:

1. Use xdebug

• Install the xdebug extension.
• Add xdebug_start_memory_dump() to the PHP file.
• Run the script and check the generated file (with the extension .xdebug).

2. Use PHPUnit

• Install PHPUnit and PHP-CodeCoverage extensions.
• Create a test class and annotate it with @after.
• Assert coverage equal to 100%.

use PHPUnit\Framework\TestCase;
use SebastianBergmann\CodeCoverage\CodeCoverage;
use SebastianBergmann\CodeCoverage\Report\{Html, Text};

class ExampleTest extends TestCase
{
    private $coverage;

    /**
     * @after
     */
    public function assertCoverage()
    {
        $this->assertEquals(1.0, $this->coverage->getCoverage());
    }

    public function testExample()
    {
        $this->coverage = new CodeCoverage();
        $this->coverage->start();
        // 执行要测试的代码
        $this->coverage->stop();
    }
}

3. Install Valgrind using Valgrind

• .
• Run php. using the
--leak-check=full
• option to check the output for memory leak reports.

Practical case

For example, the following PHP function creates a new array in each iteration of the loop:

function leakyFunction(array $input)
{
    foreach ($input as $item) {
        $output[] = $item;
    }
    return $output;
}

Using xdebug to debug this function will show the memory leak:

PHP.net\UnitTests\MemoryLeakTest : test_memory_leak_array
RESULT:

C:\build\backups\system\lib\xdebug\runtimes\libabsl.dll 000001A0205F9210  Call: __append($result, $arg)
C:\build\backups\system\lib\xdebug\runtimes\libabsl.dll 000001A0205F9210  Call: spl_object_hash($output)
C:\build\backups\system\lib\xdebug\runtimes\libabsl.dll 000001A021934520  Return: spl_object_hash($output)
C:\build\backups\PHP.net\UnitTests\MemoryLeakTest\Data\RealMemoryTestCase.php(23): __append(&xdebug_temp_1443, $item)  memory: 128 bytes allocation pinned: 0 bytes pinning overhead: 0 bytes
C:\build\backups\PHP.net\UnitTests\MemoryLeakTest\Data\RealMemoryTestCase.php(23): spl_object_hash($xdebug_temp_1443)  memory: 128 bytes allocation pinned: 0 bytes pinning overhead: 0 bytes
C:\build\backups\PHP.net\UnitTests\MemoryLeakTest\Data\RealMemoryTestCase.php(23): call_user_func_array(create_function("[&]input: ) /PHP.net/UnitTests/MemoryLeakTest/Data/RealMemoryTestCase.php(23), array($item))  memory: 96 bytes allocation pinned: 0 bytes pinning overhead: 0 bytes
C:\build\backups\PHP.net\UnitTests\MemoryLeakTest\Data\RealMemoryTestCase.php(23): call_user_func_array(create_function("[&]input: ) /PHP.net/UnitTests/MemoryLeakTest/Data/RealMemoryTestCase.php(23), array($xdebug_temp_1443))  memory: 96 bytes allocation pinned: 0 bytes pinning overhead: 0 bytes
C:\build\backups\PHP.net\UnitTests\MemoryLeakTest\Data\RealMemoryTestCase.php(23): spl_object_hash($xdebug_temp_1443)  memory: 128 bytes allocation pinned: 0 bytes pinning overhead: 0 bytes
C:\build\backups\PHP.net\UnitTests\MemoryLeakTest\Data\RealMemoryTestCase.php(23): call_user_func_array(create_function("[&]input: ) /PHP.net/UnitTests/MemoryLeakTest/Data/RealMemoryTestCase.php(23), array($item))  memory: 96 bytes allocation pinned: 0 bytes pinning overhead: 0 bytes
C:\build\backups\PHP.net\UnitTests\MemoryLeakTest\Data\RealMemoryTestCase.php(23): call_user_func_array(create_function("[&]input: ) /PHP.net/UnitTests/MemoryLeakTest/Data/RealMemoryTestCase.php(23), array($xdebug_temp_1443))  memory: 96 bytes allocation pinned: 0 bytes pinning overhead: 0 bytes

Then we can fix it:

function fixedLeakyFunction(array $input)
{
    $output = [];
    foreach ($input as $item) {
        $output[] = $item;
    }
    return $output;
}

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