php: determine where function was called from

is there a way to find out, where a function in PHP was called from? example:

function epic()
{
  fail();
}

function fail()
{
  //at this point, how do i know, that epic() has called this function?
}

Solution 1:

You can use debug_backtrace().

Example:

<?php

function epic( $a, $b )
{
    fail( $a . ' ' . $b );
}

function fail( $string )
{
    $backtrace = debug_backtrace();

    print_r( $backtrace );
}

epic( 'Hello', 'World' );

Output:

Array
(
    [0] => Array
        (
            [file] => /Users/romac/Desktop/test.php
            [line] => 5
            [function] => fail
            [args] => Array
                (
                    [0] => Hello World
                )

        )

    [1] => Array
        (
            [file] => /Users/romac/Desktop/test.php
            [line] => 15
            [function] => epic
            [args] => Array
                (
                    [0] => Hello
                    [1] => World
                )

        )

)

Solution 2:

Use debug_backtrace():

function fail()
{
    $backtrace = debug_backtrace();

    // Here, $backtrace[0] points to fail(), so we'll look in $backtrace[1] instead
    if (isset($backtrace[1]['function']) && $backtrace[1]['function'] == 'epic')
    {
        // Called by epic()...
    }
}

Solution 3:

Fastest and simplest solution as I found

public function func() { //function whose call file you want to find
    $trace = debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS, 1);
}

$trace: Array
(
    [0] => Array
        (
            [file] => C:\wamp\www\index.php
            [line] => 56
            [function] => func
            [class] => (func Class namespace)
            [type] => ->
        )

)

I test the speed on Lenovo laptop: Intel Pentiom CPU N3530 2.16GHz, RAM 8GB

global $times;
$start = microtime(true);
$trace = debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS, 1);
$times[] = microtime(true) - $start;

Results:

count($times):  97
min:    2.6941299438477E-5
max:   10.68115234375E-5
avg:    3.3095939872191E-5
median: 3.0517578125E-5
sum:  321.03061676025E-5

the same results with notation without E-5
count($times):  97
min:    0.000026941299438477
max:    0.0001068115234375
avg:    0.000033095939872191
median: 0.000030517578125
sum:    0.0032103061676025