PHP 5.2.x array operation details sharing

$arr = array("a" => 1,"b" => 2,"c" => 3);

If Defining an array like this will result in a compilation error:

$arr = array("a" = 1,"b" = 2,"c" = 3);

Therefore, when defining the array Can only be used => 2,

$arr = array("a" => 1,"b" => 2,"c" => 3);
echo $arr[0];
 echo $arr[1];

The result will be blank.

Correct printing method:

echo $arr["a"];

3. When adding elements or modifying elements, you can only use =, not =>

$arr = array("a" => 1,"b" => 2,"c" => 3);
$arr["c"] = > 6;

The above operation method will cause a compilation error in php 5.2.5

To add elements or modify elements, write like this:

$arr = array("a" => 1,"b" => 2,"c" => 3);
$arr["d"] = 4;
$arr["c"] = 6;

To delete elements, use unset:

unset ($arr["c"]);

4. Think about the following code, what will be output?

$arr = array("a" => 1,2,"b" => 3,4);
$arr[] = 5;
foreach($arr as $key => $value)
{
 echo "key:$key value:$value";
}

Output result:

$arr = array("a" => 1,3,"b" => 2);
//After creating the array, the default pointer points to the first element
echo current($arr)."";
//Go forward one position
echo next($arr)."";
//The default principle of sorting is from small to large
sort( $arr);
//After finishing, the array pointer stops at the first element
echo current($arr)."";
echo next($arr)."";
 //Go back one position
echo prev($arr)."";

Output result: 1 3 1 2 1