PHP error messages are quite helpful, most of the time. Sometimes they do fall short of telling us what went wrong, however. It’s especially common when and if you use a development framework (e.g. Drupal). Frameworks often do output buffering and/or code eval()-ing, making debugger output incomprehensible.

In such cases PHP’s debug_backtrace() function is a real savior. debug_backtrace() is also very helpful if you want to look at the execution stack in a complicated code, to better understand the code. This function shows the execution stack that lead to the current function and does it pretty well… “too well” sometimes :) Out-of-the-box version of the function shows the list of invoked functions, source files they belong to, line numbers in the source file and the argument values being passed. The latter can be a huge problem, if code is passing around large variables. Output on the screen may get so garbled (esp. if HTML is used in variables) that the entire exercise may lose its meaning.

Short snippet below sanitizes debug_backtrace() output to make it slimmer and more comprehensible:

$trace = debug_backtrace();
foreach ($trace as &$t) {
echo "<pre>".print_r ( $trace,true)."</pre>";