Starting with the version 5.3, PHP introduced
Anonymous functions, known as
Closures.
This type of functions have no specified name. They are most useful as the value of callback.
1. Example, Anonymous function as callback function.
<?php
$arr = array(' hello word ', ' Have <b>good day</b>');
// removes tags and whitespace from the beginning and end of each array element
// capitalize the first character of each word
$arr = array_map(function($elm){
return ucwords(trim(strip_tags($elm)));
}, $arr);
var_export($arr); // array ( 0 => 'Hello Word', 1 => 'Have Good Day' )
?>
2. Closures can also be used as the values of variables (
notice how the function is called, using the variable name, including the $ character).
<?php
$website = function($name) {
return 'http://www.'. $name. '.net';
};
echo $website('coursesweb'); // https://coursesweb.net
echo $website('marplo'); // https://marplo.net
?>
3. Closures can also be used inside another function. In the following example it is used closures to create HTML List elements.
<?php
// receives an array with elements that will form the <li>
function ulList($ar_items) {
$li = function($item) {
return '<li>'. $item. '</li>';
};
// traverse the array received in parameter, calls $li() to create the <ul><li>
$ul = '<ul>';
foreach($ar_items as $item) {
$ul .= $li($item);
}
$ul .= '<ul>';
return $ul;
}
$ar_items = array('li 1', 'li 2', 'li 3');
echo ulList($ar_items); // <ul><li>li 1</li><li>li 2</li><li>li 3</li><ul>
?>
- Another example with anonymous function inside other function. Notice the using of the
use() , to can use the outside variables inside anonymous function.
<?php
function test($a) {
$b = $a / 2;
$c = function($a) use($b) {
return $a + $b;
};
return $c($a);
}
echo test(10); // 15
?>
4. Closures can be a useful tool for object-oriented programming. Starting with PHP 5.4 ,
$this can be used in anonymous functions.
<?php
class A {
private $value = 1;
public function getVal() {
return function() { return $this->value * 2; };
}
}
$a = new A;
echo $a->getVal(); // 2
?>
Daily Test with Code Example
HTML
CSS
JavaScript
PHP-MySQL
Which meta tag provides a short description of the page?
<meta content="..."> <meta description="..."> <meta http-equiv="..."><meta name="description" content="70-160 characters that describes the content of the page" />
Which CSS property is used to stop the wrapping effect of the "float"?
clear text-align position#some_id {
clear: both;
}
Click on the method which gets an array with all the elements in the document that have a specified tag name.
getElementsByName() getElementById() getElementsByTagName()var divs = document.getElementsByTagName("div");
var nr_divs = divs.length;
alert(nr_divs);
Indicate the PHP function which returns the number of elements in array.
is_[) count() strlen()$arr =[7, 8, "abc", 10);
$nri = count($arr);
echo $nri; // 4