--TEST--
Test array_filter() function : usage variations - built-in functions as 'callback' argument 
--FILE--
<?php
/* Prototype  : array array_filter(array $input [, callback $callback])
 * Description: Filters elements from the array via the callback. 
 * Source code: ext/standard/array.c
*/

/*
* Passing built-in functions and different language constructs as 'callback' argument
*/

echo "*** Testing array_filter() : usage variations - built-in functions as 'callback' argument ***\n";

$input = array(0, 1, -1, 10, 100, 1000, 'Hello', null);

// using built-in function 'is_int' as 'callback'
var_dump( array_filter($input, 'is_int') );

// using built-in function 'chr' as 'callback'
var_dump( array_filter($input, 'chr') );

// using language construct 'echo' as 'callback'
var_dump( array_filter($input, 'echo') );

// using language construct 'exit' as 'callback' 
var_dump( array_filter($input, 'exit') );

echo "Done"
?>
--EXPECTF--
*** Testing array_filter() : usage variations - built-in functions as 'callback' argument ***
array(6) {
  [0]=>
  int(0)
  [1]=>
  int(1)
  [2]=>
  int(-1)
  [3]=>
  int(10)
  [4]=>
  int(100)
  [5]=>
  int(1000)
}
array(8) {
  [0]=>
  int(0)
  [1]=>
  int(1)
  [2]=>
  int(-1)
  [3]=>
  int(10)
  [4]=>
  int(100)
  [5]=>
  int(1000)
  [6]=>
  string(5) "Hello"
  [7]=>
  NULL
}

Warning: array_filter() expects parameter 2 to be a valid callback, function 'echo' not found or invalid function name in %s on line %d
NULL

Warning: array_filter() expects parameter 2 to be a valid callback, function 'exit' not found or invalid function name in %s on line %d
NULL
Done