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Unit 7: Multidimensional Arrays

The array_search( ) function also takes the optional third strict argument, which requires the Notes
types of the value being searched for and the value in the array to match.

Develop a PHP program to build a table with the iterator functions.

7.5 Sorting of Multidimensional Arrays

Sorting arrays with more than one dimension, or by something other than alphabetical or
numerical order, is more complicated. PHP knows how to compare two numbers or two text
strings, but in a multidimensional array, each element is an array. PHP does not know how to
compare two arrays, so you need to create a method to compare them. Most of the time, the
order of the words or numbers is fairly obvious but for complicated objects, it becomes more
problematic.

7.5.1 User Defined Sorts
Here is the definition of a two-dimensional array we used earlier. This array stores three products
with a code, a description, and a price for each.
$products = array( array( ‘TIR’, ‘Tires’, 100 ),
array( ‘OIL’, ‘Oil’, 10 ),

array( ‘SPK’, ‘Spark Plugs’, 4 ) );
If we sort this array, what order will the values end up in? Because we know what the contents
represent, there are at least two useful orders. We might want the products sorted into alphabetical
order using the description or by numeric order by the price. Either result is possible, but we
need to use the function usort() and tell PHP how to compare the items. To do this, we need to
write our own comparison function.
The following code sorts this array into alphabetical order using the second column in the array
the description.
function compare($x, $y)
{

if ( $x[1] == $y[1] )
return 0;

else if ( $x[1] < $y[1] )
return -1;
else

return 1;
}
usort($products, ‘compare’);

So far in this book, we have called a number of the built-in PHP functions. To sort this array,
we have defined a function of our own.

We define a function using the keyword function. We need to give the function a name. Names
should be meaningful, so we’ll call it compare (). Many functions take parameters or arguments.

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