Variable functions
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(), print(), unset(), isset(), empty(), include(),
require() and the like. You need to use your own wrapper
function to utilize any of these constructs as variable
functions.
Example 12-12. Variable function example
<?php
function foo() {
echo "In foo()<br />\n";
}
function bar($arg = '')
{
echo "In bar(); argument was '$arg'.<br />\n";
}
// This is a wrapper function around echo
function echoit($string)
{
echo $string;
}
$func = 'foo';
$func(); // This calls foo()
$func = 'bar';
$func('test'); // This calls bar()
$func = 'echoit';
$func('test'); // This calls echoit()
?>
You can also call an object's method by using the variable
functions feature.
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