 Re: Using Arrays in PHP
Storing Data in Arrays
Storing a value in an array will create the array if it didn't already exist, but trying to retrieve a value from an array that hasn't been defined yet won't create the array. For example:
// $addresses not defined before this point
echo $addresses[0]; // prints nothing
echo $addresses; // prints nothing
$addresses[0] = 'spam@cyberpromo.net';
echo $addresses; // prints "Array"
Using simple assignment to initialize an array in your program leads to code like this:
$addresses[0] = 'spam@cyberpromo.net';
$addresses[1] = 'abuse@example.com';
$addresses[2] = 'root@example.com';
// ...
That's an indexed array, with integer indexes beginning at 0. Here's an associative array:
$price['Gasket'] = 15.29;
$price['Wheel'] = 75.25;
$price['Tire'] = 50.00;
// ...
An easier way to initialize an array is to use the array( ) construct, which builds an array from its arguments. This builds an indexed array, and the index values (starting at 0) are created automatically:
$addresses = array('spam@cyberpromo.net', 'abuse@example.com',
'root@example.com');
To create an associative array with array( ), use the => symbol to separate indexes from values:
$price = array('Gasket' => 15.29,
'Wheel' => 75.25,
'Tire' => 50.00);
Notice the use of whitespace and alignment. We could have bunched up the code, but it wouldn't have been as easy to read:
$price = array('Gasket'=>15.29,'Wheel'=>75.25,'Tire'=>50.00 );
To construct an empty array, pass no arguments to array( ):
$addresses = array( );
You can specify an initial key with => and then a list of values. The values are inserted into the array starting with that key, with subsequent values having sequential keys:
$days = array(1 => 'Monday', 'Tuesday', 'Wednesday',
'Thursday', 'Friday', 'Saturday', 'Sunday');
// 2 is Tuesday, 3 is Wednesday, etc.
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