This code does not understand how to sort arrays.

This code does not understand how to sort arrays. At the end of this post, a two-dimensional array is edited and defined by baidu_24894285 at 2015-01-2620: 32: 24, and two functions are customized, the first one sorts the second column in the array in ascending order of letters, and the second function sorts the third column in the array in ascending order of numbers. What I don't understand is that these two UDFs are so strange that I don't understand this code.

This post was last edited by baidu_24894285 on 20:32:24

Defines a two-dimensional array, and then customizes two functions. The first one sorts the second column in the array in ascending order of letters, and the second function sorts the third column in the array.
The numbers are listed in ascending order.
What I don't understand is how strange these two UDFs are. what does $ x $ y in them represent? how can we compare them with others? Which of the following heroes can explain in detail the logical structure.

$ Products = array ('tire', 'tires', '123 '),
Array ('oil ', 'Oil', '10 '),
Array ('spk', 'spark S s', '4 ')
);


Var_dump ($ products );

Function compare1 ($ x, $ y ){
If ($ x [1] ==$ y [1]) {
Return 0;
} Elseif ($ x [1] <$ y [1]) {
Return-1;
}
Else {
Return 1;
}
}

Usort ($ products, 'company1 ');
Var_dump ($ products );

Function compare2 ($ x, $ y ){
If ($ x [2] = $ y [2]) {
Return 0;
} Elseif ($ x [2] <$ y [2]) {
Return-1;
}
Else {
Return 1;
}
}

Usort ($ products, 'company2 ');
Var_dump ($ products );
?>


Print result:
Array (size = 3)
0 =>
Array (size = 3)
0 => string 'core' (length = 3)
1 => string 'tires' (length = 5)
2 => string '20140901' (length = 3)
1 =>
Array (size = 3)
0 => string 'oil '(length = 3)
1 => string 'oil '(length = 3)
2 => string '10' (length = 2)
2 =>
Array (size = 3)
0 => string 'spk' (length = 3)
1 => string 'spark S s' (length = 11)
2 => string '4' (length = 1)

Array (size = 3)
0 =>
Array (size = 3)
0 => string 'oil '(length = 3)
1 => string 'oil '(length = 3)
2 => string '10' (length = 2)
1 =>
Array (size = 3)
0 => string 'spk' (length = 3)
1 => string 'spark S s' (length = 11)
2 => string '4' (length = 1)
2 =>
Array (size = 3)
0 => string 'core' (length = 3)
1 => string 'tires' (length = 5)
2 => string '20140901' (length = 3)

Array (size = 3)
0 =>
Array (size = 3)
0 => string 'spk' (length = 3)
1 => string 'spark S s' (length = 11)
2 => string '4' (length = 1)
1 =>
Array (size = 3)
0 => string 'oil '(length = 3)
1 => string 'oil '(length = 3)
2 => string '10' (length = 2)
2 =>
Array (size = 3)
0 => string 'core' (length = 3)
1 => string 'tires' (length = 5)
2 => string '20140901' (length = 3)

------ Solution ----------------------
Take a look at the second parameter description of the usort method in the manual:
Cmp_function
When the first parameter is less than, equal to, or greater than the second parameter, the comparison function must return an integer less than, equal to, or greater than 0.
Int callback (mixed $ a, mixed $ B)

It is easy to understand that $ a and $ B are the elements currently used for comparison in the array. In your example
Array ('tire', 'tires', '123 ')
Array ('oil ', 'Oil', '10 '),
Array ('spk', 'spark S s', '4 ')

In fact, if you want to know what $ a and $ B are, print them out.

$products = array(  array('TIR','tires','100'),
array('OIL','oil','10'),
array('SPK','spark plugs','4')
);

function compare1($x,$y){
    echo 'x:';
    var_dump($x);
    echo 'y:';
    var_dump($y);

    if ($x[1] == $y[1]) {
        return 0;
    }elseif ($x[1]<$y[1]) {
        return -1;
    }
        else{
    return 1;
    }
}

usort($products,'compare1');

x:
array (size=3)
  0 => string 'OIL' (length=3)
  1 => string 'oil' (length=3)
  2 => string '10' (length=2)
y:
array (size=3)
  0 => string 'TIR' (length=3)
  1 => string 'tires' (length=5)
  2 => string '100' (length=3)
x:
array (size=3)
  0 => string 'SPK' (length=3)
  1 => string 'spark plugs' (length=11)
  2 => string '4' (length=1)
y:
array (size=3)
  0 => string 'OIL' (length=3)
  1 => string 'oil' (length=3)
  2 => string '10' (length=2)
x:
array (size=3)
  0 => string 'TIR' (length=3)
  1 => string 'tires' (length=5)
  2 => string '100' (length=3)
y:
array (size=3)
  0 => string 'OIL' (length=3)
  1 => string 'oil' (length=3)
  2 => string '10' (length=2)
x:
array (size=3)
  0 => string 'SPK' (length=3)
  1 => string 'spark plugs' (length=11)
  2 => string '4' (length=1)
y:
array (size=3)
  0 => string 'TIR' (length=3)
  1 => string 'tires' (length=5)
  2 => string '100' (length=3)