var func = function(){
  alert('hello!');
};

func.call();

Solution:

function theFunction(name, profession) {
    console.log("My name is " + name + " and I am a " + profession + ".");
}
theFunction("John", "fireman");
theFunction.apply(undefined, ["Susan", "school teacher"]);
theFunction.call(undefined, "Claude", "mathematician");
theFunction.call(undefined, ...["Matthew", "physicist"]); // used with the spread operator

// Output: 

// My name is John and I am a fireman.
// My name is Susan and I am a school teacher.
// My name is Claude and I am a mathematician.
// My name is Matthew and I am a physicist.

var functionOne = function() {
    // Some code
};

function functionTwo() {
    // Some code
}

Answer :

// TypeError: undefined is not a function
functionOne();

var functionOne = function() {
  console.log("Hello!");
};

// Outputs: "Hello!"
functionTwo();

function functionTwo() {
  console.log("Hello!");
}

if (test) {
   // Error or misbehavior
   function functionThree() { doSomething(); }
}

Answer :

<?php
    $functions = array();
    $path = "/path/to/my/php/project";
    define_dir($path, $functions);
    reference_dir($path, $functions);
    echo
        "<table>" .
            "<tr>" .
                "<th>Name</th>" .
                "<th>Defined</th>" .
                "<th>Referenced</th>" .
            "</tr>";
    foreach ($functions as $name => $value) {
        echo
            "<tr>" . 
                "<td>" . htmlentities($name) . "</td>" .
                "<td>" . (isset($value[0]) ? count($value[0]) : "-") . "</td>" .
                "<td>" . (isset($value[1]) ? count($value[1]) : "-") . "</td>" .
            "</tr>";
    }
    echo "</table>";
    function define_dir($path, &$functions) {
        if ($dir = opendir($path)) {
            while (($file = readdir($dir)) !== false) {
                if (substr($file, 0, 1) == ".") continue;
                if (is_dir($path . "/" . $file)) {
                    define_dir($path . "/" . $file, $functions);
                } else {
                    if (substr($file, - 4, 4) != ".php") continue;
                    define_file($path . "/" . $file, $functions);
                }
            }
        }       
    }
    function define_file($path, &$functions) {
        $tokens = token_get_all(file_get_contents($path));
        for ($i = 0; $i < count($tokens); $i++) {
            $token = $tokens[$i];
            if (is_array($token)) {
                if ($token[0] != T_FUNCTION) continue;
                $i++;
                $token = $tokens[$i];
                if ($token[0] != T_WHITESPACE) die("T_WHITESPACE");
                $i++;
                $token = $tokens[$i];
                if ($token[0] != T_STRING) die("T_STRING");
                $functions[$token[1]][0][] = array($path, $token[2]);
            }
        }
    }
    function reference_dir($path, &$functions) {
        if ($dir = opendir($path)) {
            while (($file = readdir($dir)) !== false) {
                if (substr($file, 0, 1) == ".") continue;
                if (is_dir($path . "/" . $file)) {
                    reference_dir($path . "/" . $file, $functions);
                } else {
                    if (substr($file, - 4, 4) != ".php") continue;
                    reference_file($path . "/" . $file, $functions);
                }
            }
        }       
    }
    function reference_file($path, &$functions) {
        $tokens = token_get_all(file_get_contents($path));
        for ($i = 0; $i < count($tokens); $i++) {
            $token = $tokens[$i];
            if (is_array($token)) {
                if ($token[0] != T_STRING) continue;
                if ($tokens[$i + 1] != "(") continue;
                $functions[$token[1]][1][] = array($path, $token[2]);
            }
        }
    }
?>