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8 years ago
Calling restore_error_handler from within an error handler might result in unexpected behaviour:

<?php
error_reporting(0);

set_error_handler('handleError1');
trigger_error('1-stack:h1');

set_error_handler('handleError2');
trigger_error('2-stack:h1,h2');

trigger_error('6-stack:h1,h2');
trigger_error('7-stack:h1,h2');

function handleError1($code, $message, $file = '', $line = 0, $context = array())
{
    echo  __METHOD__ . ' ' . $message . PHP_EOL;
}

function handleError2($code, $message, $file = '', $line = 0, $context = array())
{
    trigger_error('3-DEFAULT'); // This will use the php's default error handler

    echo  __METHOD__ . ' ' . $message . PHP_EOL;

    set_error_handler('handleError3');
    trigger_error('4-stack:h1,h2,h3');

    restore_error_handler(); // This will restore the handleError1 instead of the default error handler
    trigger_error('5-DEFAULT');
}

function handleError3($code, $message, $file = '', $line = 0, $context = array())
{
    echo  __METHOD__ . ' ' . $message . PHP_EOL;
}

?>

The above code will output:

handleError1 1-stack:h1
handleError2 2-stack:h1,h2
handleError3 4-stack:h1,h2,h3
handleError1 5-DEFAULT
handleError1 6-stack:h1,h2
handleError1 7-stack:h1,h2

The following workaround can be used:

<?php

error_reporting(0);

set_error_handler('handleError1');
trigger_error('1-stack:h1');

set_error_handler('handleError2');
trigger_error('2-stack:h1,h2');

trigger_error('6-stack:h1,h2');
trigger_error('7-stack:h1,h2');

function handleError1($code, $message, $file = '', $line = 0, $context = array())
{
    echo __METHOD__ . ' ' . $message . PHP_EOL;
}

function handleError2($code, $message, $file = '', $line = 0, $context = [])
{
    restore_error_handler(); // This will restore the previous error handler
    set_error_handler('count', 0); // Set a dummy method for error handling, it will never be called because $error_type = 0
    try
    {
        trigger_error('3-DEFAULT');

        echo __METHOD__ . ' ' . $message . PHP_EOL;

        set_error_handler('handleError3');
        trigger_error('4-stack:h1,h2,h3');

        restore_error_handler();
        trigger_error('5-DEFAULT');
    }
    finally
    {
        restore_error_handler(); // Restore the previous error handler
        set_error_handler('handleError2'); // Set the current error handler again
    }
}

function handleError3($code, $message, $file = '', $line = 0, $context = [])
{
    echo __METHOD__ . ' ' . $message . PHP_EOL;
}
?>

which will output:

handleError1 1-stack:h1
handleError2 2-stack:h1,h2
handleError3 4-stack:h1,h2,h3
handleError2 6-stack:h1,h2
handleError3 4-stack:h1,h2,h3
handleError2 7-stack:h1,h2
handleError3 4-stack:h1,h2,h3
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