usort($arr, 'mySortFunc');
//回调方法在对象中
usort($arr, array($objectName, 'mySortFunc'));
//回调方法在类的静态方法里
usort($arr, array('ClassName', 'mySortFunc'));
usort($arr, array('ClassName::mySortFunc'));
//通过子类调用父类中的方法(很少用)
usort($arr, array('Child', 'parent::mySort'));
usort($arr, function($a, $b) {
return $b - $a;
$string = "Hello World!\n";
$closure = function() use ($string) {
echo $string;
};
$string = "Hello China\n";
$closure();
$string = "Hello China\n";
function getPrinter(&$string) {
return function() use($string) {
echo $string;
};
}
$printer = getPrinter($string);
$string = "Hello Cat\n";
$printer();
<?php
function test($str) {
echo $str;
}
echo is_callable('test');
call_user_func('test', 'param1');
call_user_func_array('test', ['param1']);