Challenge for ZEND PHP5 Certification - 025

[hinom 5]

Exercise 25

 

Variable functions in PHP don't work directly with:

 

A. echo()

B. isset()

C. print()

D. All of the above

[hinom 5]

Answer: D

 

Explanation

 

Variable functions won't work with language constructs such as echo(), print(), unset(), isset(), empty(), include(), require() and the like. Utilize wrapper functions to make use of any of these constructs as variable functions.

<?php
function foo() {
	echo "bar";
}

$func = 'foo';
$func();		// This calls foo()
?>

 

<?php
$func = 'rand';
echo $func(1,5);		// This calls rand()
?>

 

<?php
$func = 'echo';
$func('foo bar');		// This is invalid
?>

http://php.net/manual/functions.variable-functions.php