How to create an array in php and fill an array

$arr = array('a','b','c');
$arr[] = 'a' ; $arr[] = 'b' ; $arr[] = 'c';
$arr = array('name' => '关羽' , 'age' => 23 , 'sex' => '男')；

$number = range(0,5); 
print_r ($number); 

//打印：Array ( [0] => 0 [1] => 1 [2] => 2 [3] => 3 [4] => 4 [5] => 5 ) 

$number = range(0,50,10); 
print_r ($number); 

//打印：Array ( [0] => 0 [1] => 10 [2] => 20 [3] => 30 [4] => 40 [5] => 50 ) 

$letter = range("a","d"); 
print_r ($letter); 

//打印：Array ( [0] => a [1] => b [2] => c [3] => d )

$firstname = "Peter"; 
$lastname = "Griffin"; 
$age = "38"; 
$result = compact("firstname", "lastname", "age"); 
print_r($result); 

//打印： Array ( [firstname] => Peter [lastname] => Griffin [age] => 38 ) 

$firstname = "Peter"; 
$lastname = "Griffin"; 
$age = "38"; 
$name = array("firstname", "lastname"); 
$result = compact($name, "location", "age"); 
print_r($result); 

//打印：Array ( [firstname] => Peter [lastname] => Griffin [age] => 38 ) 
//由于$location变量不存在，所以存入不了数组

$a1=array("a","b","c","d"); 
$a2=array("Cat","Dog","Horse","Cow"); 
print_r(array_combine($a1,$a2)); 

//打印：Array ( [a] => Cat [b] => Dog [c] => Horse [d] => Cow )

$a=array_fill(2,3,"Dog"); 
print_r($a); 

//打印：Array ( [2] => Dog [3] => Dog [4] => Dog )