我如何获取字符串数组的两个连续值的值

Question

I want to sort elements of an array which have string values (word) according to word length. I am performing insertion sort:

$str="welcome to php";
 $st=explode(" ",$str);
   $a=count($st);
    for($i=0;$i<$a;$i++)
     {
       for($j=0;$j<$a;$j++)
        {
          if(strlen($st[$j])<strlen($st[$j+1]))
               {$t=$st[$j];
                 $st[$j]=$st[$j+1];
                 $st[$j+1]=$t;}
   }}

So the problem is $st[$j+1] . It doesn't get next value of array. It gives undefined offset. How can I get next value of array?

Answer 1

Somthing like this should work for you:

<?php

    function lengthSort($a, $b){
        return strlen($b) - strlen($a);
    }

    $str = "welcome to php";
    $st = explode(" ", $str);

    usort($st,'lengthSort');
    var_dump($st);

?>

Output:

array(3) {
  [0]=>
  string(7) "welcome"
  [1]=>
  string(3) "php"
  [2]=>
  string(2) "to"
}

Also as Nick J suggested take a look at the foreach loop! It's very powerful!

Answer 2

You can define your own comparison function using php's usort function.

See http://php.net/manual/en/function.usort.php

So all you have to do is write your own function that compares strings by their length, then call usort and pass in your function.