﻿ PHP Array Exercise: Sort an array according to another array as a priority list - w3resource

# PHP Array Exercises : Sort an array according to another array as a priority list

## PHP Array: Exercise-20 with Solution

Write a PHP function to sort an array according to another array acting as a priority list.

Sample Solution:

PHP Code:

``````<?php
// Define a function named 'list_cmp' that compares two values based on their order in the global array '\$order'
function list_cmp(\$a, \$b)
{
global \$order;

// Iterate through the '\$order' array
foreach (\$order as \$key => \$value)
{
// If \$a matches a value in '\$order', return 0 to indicate equality
if (\$a == \$value)
{
return 0;
break;
}

// If \$b matches a value in '\$order', return 1 to indicate inequality
if (\$b == \$value)
{
return 1;
break;
}
}
}

// Define an array '\$order' specifying the desired order of values
\$order[0] = 1;
\$order[1] = 3;
\$order[2] = 4;
\$order[3] = 2;

// Define an array '\$array' with unsorted values
\$array[0] = 2;
\$array[1] = 1;
\$array[2] = 3;
\$array[3] = 4;
\$array[4] = 2;
\$array[5] = 1;
\$array[6] = 2;

// Use 'usort' function to sort '\$array' based on the order specified in the 'list_cmp' function
usort(\$array, "list_cmp");

// Print the sorted array
print_r(\$array);
?>
```
```

Output:

```Array
(
[0] => 1
[1] => 1
[2] => 3
[3] => 4
[4] => 2
[5] => 2
[6] => 2
)
```

Flowchart:

PHP Code Editor:

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