English
English
In PHP, the ob_list_handlers function is a tool for getting all cache handlers in the current output buffer manager (OB). Through it, you can track the call stack of cache handlers, helping you better debug and understand the execution process of output caches. This article will explain how to use ob_list_handlers to debug the call stack of PHP cache handlers and provide some sample code.
In PHP, output cache is a mechanism for temporarily storing output content into memory, allowing you to capture output during script execution rather than sending it directly to the browser. This is very useful for reducing the performance overhead of multiple output operations, or for performing content processing (such as compression, modification, etc.). PHP provides multiple functions to control the behavior of output cache, such as ob_start() , ob_end_flush() , ob_flush() , etc.
The function of the ob_list_handlers function is to return all current output cache handlers. These handlers include cache handlers created by ob_start() . You can use this function to get a list of cache stacks to understand how caches are processed in order.
<?php
// Start the output cache
ob_start();
// Add a custom cache handler
ob_start(function($buffer) {
return strtoupper($buffer); // Convert output to uppercase
});
// pass ob_list_handlers Get the list of current cache handlers
$handlers = ob_list_handlers();
echo "Current cache handler:\n";
print_r($handlers);
// Output some content
echo "This is a test string。";
// Get and print all handlers
$handlers = ob_list_handlers();
echo "Current cache handler（Call again ob_list_handlers）:\n";
print_r($handlers);
// End cache and output
ob_end_flush();
// End cache
ob_end_clean();
?>
ob_start() : Start an output cache. When no handler is specified, PHP uses the default caching mechanism.
ob_start(function($buffer) {...}) : Specifies a custom cache handler to convert the output content to uppercase.
ob_list_handlers() : Returns a list of all current output cache handlers, and can view the current cached processing stack.
ob_end_flush() : End cache and output the contents of the buffer to the browser.
ob_end_clean() : End cache and discard buffer content.
In the above code, you can view the current list of output cache handlers using ob_list_handlers() . Each time the function is called, you will see an array containing all the cache handlers currently activated.
Current cache handler:
Array
(
[0] => no-processor
[1] => closure
)
Current cache handler（Call again ob_list_handlers）:
Array
(
[0] => closure
)
In the example above, we can see the stack of the current cache handler. The first call to ob_list_handlers() returns a default "no-processor" ( no-processor ), while the second call shows the handler we added ourselves ( closure ). This means that the cache stack will change according to the order of call.
In complex PHP applications, multiple cache handlers may be called in sequence. Using ob_list_handlers allows you to view the order of cache handlers in real time, helping you debug cache issues. For example, when you encounter that the cache content is not processed as expected, you can check the cache handler stack to confirm whether there are any handlers missing or the order of execution errors.
Suppose you are developing a PHP website and cache some dynamic content. But you find that the cached content is not processed as expected, such as not compressed or modified correctly. At this point, you can use ob_list_handlers() to print out the cache stack and check if there are multiple output cache handlers, or some handlers are not applied correctly.
<?php
// Start an output cache and apply multiple handlers
ob_start(function($buffer) {
return strrev($buffer); // Reverse the output content
});
ob_start(function($buffer) {
return strtoupper($buffer); // Convert output to uppercase
});
// View the current cache handler
$handlers = ob_list_handlers();
print_r($handlers);
// Output content
echo "This is a test string。";
// End cache and output
ob_end_flush();
?>
In this example, ob_list_handlers() will show the order of inversion and capitalization handlers. This way, you can easily check and debug the handler of the PHP output cache.
