PHP's judgment results about empty and isset parameters

<?php
	class test{}
	$a1 = null;
	$a2 = "";
	//$a3 = 
	$a4 = 0;
	$a5 = '0';
	$a6 = false;
	$a7 = array();
	//var $a8;
	$a9 = new test();

	for ($i=1; $i <=9 ; $i++) { 
		$s = 'a'.$i;
		echo $i . ":";
		var_dump(isset($$s));
		echo '<br />';

	}
	echo '<br />';
	for ($i=1; $i <=9 ; $i++) { 
		$s = 'a'.$i;
		echo $i . ":";
		var_dump(empty($$s));
		echo '<br />';
	}

That’s basically it

The above introduces the PHP judgment results of empty and isset parameters, including the content. I hope it will be helpful to friends who are interested in PHP tutorials.