如何获得此PHP脚本的输出？

Question

I'm a newbie to programming and PHP learning about two dimensional arrays.

When I run this code below, it just gives me a blank page. When I put an echo in front of the function call like this echo usort($a, 'mysort1'); the page shows me a 1 (I have no idea why).

What I really want to see is the output of the array after it's been sorted.

Doing var_dump($a); is not what I'm after. how do I show the result of the function?

How? Thanks if you can help.

<?php

$a = array (
array ('key1' => 940, 'key2' => 'blah'),
array ('key1' => 23, 'key2' => 'this'),
array ('key1' => 894, 'key2' => 'that')
);


function mysort1($x, $x) {
     return ($x['key1'] > $y['key']);

}

usort($a, 'mysort1'); 


?> 

Answer 1

For starters I think you have two typos in your comparison function:

                     //should be $y not $x
function mysort1($x, $y) {
     return ($x['key1'] > $y['key1']);  // Should be $y['key1']
}

Next, usort sorts the array in place returning TRUE on success and FALSE otherwise, that is why you see a 1 when you echo it's return value.

Try:

print_r($a);

to display the sorted array.

Answer 2

Put this as the last line... var_dump($a); it is a quick way to see what is in an array.

Answer 3

Add this:

print_r($a);

after your usort

If you want to output the data nicely using HTML, you could use a foreach loop as follows:

echo "<ul>";
foreach ($a as $key => $value)
{
    echo "<li>key: ", $key, " value: ", $value, "</li>";
}
echo "</ul>";

Or something similar with tables if you like.

usort actually sorts the array you pass to it. In other words, it does not return a sorted array but performs the sort on the same array you pass it because it's passing by reference. If you look here: http://php.net/manual/en/function.usort.php you will see there is an ampersand infront of the parameter. The return value of usort indicates success or failure. Again, you can see this in the manual.

Answer 4

You are printing the return value of the function usort , and not the contents of your array. Instead try giving print_r a shot after calling usort.

Answer 5

Add after the usort line

var_dump( $a );

Your page only prints "1" because it is saying that usort was successful in sorting the array.