PHP supports the concept of variable functions. This means that if
a variable name has parentheses appended to it, PHP will look for
a function with the same name as whatever the variable evaluates
to, and will attempt to execute it. Among other things, this can
be used to implement callbacks, function tables, and so forth.
Variable functions won't work with language constructs such
as echo(), unset(),
isset(), empty() and
include(). Although, the construct
print() is an exception and will work.
This is one of the major differences between PHP functions and
language constructs.
Example 12-1. Variable function example <?php
function foo()
{
echo "In foo()<br>\n";
}
function bar($arg = '')
{
echo "In bar(); argument was '$arg'.<br>\n";
}
$func = 'foo';
$func();
$func = 'bar';
$func('test');
?> |
|
See also
variable variables and function_exists().
