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Lessons PHP Array Types Bookmark and Share
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Lesson 44
We can classify PHP arrays in three different types:

1. Numeric Arrays
2. Associative Arrays
3. Multidimensional Arrays

1. Numeric Arrays
A numeric array stores each element with a numeric ID key. The arrays we saw in the last lesson, were examples of numeric arrays. As we learned in the last lesson, there are two ways to create a numeric array, as shown in the following examples:

Example 1
$days = array("Friday", "Saturday", "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday");
//PHP automatically provides numeric ID keys

Example 2

$days[0] = "Friday";
$days[1] = "Saturday";
$days[2] = "Sunday";
$days[3] = "Monday";
$days[4] = "Tuesday";
$days[5] = "Wednesday";
$days[6] = "Thursday";
//programmer provides numeric keys

Using the above arrays is very simple. We use $variableName[index] notation to access array elements. For example to output the sixth element of the $days array above:

echo $days[5];

2. Associative Arrays
In an associative array, each ID key is associated with a value. An index is always numeric, while a key could be a string too. An associative array stores a key, value pair. Internally PHP stores two arrays, one containing the keys, and the other containing values. PHP associates these arrays as key, value pairs, hence the name associative arrays. Like a numeric array, we can create an associative array in two ways, as shown in the following examples:

Example 1
$acronyms = array("PHP"=>"PHP: Hypertext Preprocessor", "SQL"=>"Standard Query Language", "HTML"=>"HyperText Markup Language");

echo $acronyms["PHP"]; // prints PHP: Hypertext Preprocessor

The above exmple declares an associative array. Notice the => sign. On the left side of the => sign we provide the key and on the right side of the => is the value. When accessing the array we use the notation [Key].

Example 2
$acronyms['PHP'] = "PHP: Hypertext Preprocessor";
$acronyms['SQL'] = "Standard Query Language";
$acronyms['HTML'] = "HyperText Markup Language";
echo $acronyms["SQL"]; // prints Standard Query Language

3. Multidimensional Arrays
A multidimensional array can be defined as an array of arrays. In a multidimensional array, each element in the main array can be an array, and each element in the sub-array can also be an array, and so on. In the following example we create a multidimensional array:
$countryCities = array
"Saudi Arabia"=>array
Accessing elements of a multidimensional array is very simple. Consider the following code:

echo $countryCities['Saudi Arabia'][0]; // outputs Makkah

Notice the use of [][] above. $countryCities is a two dimensional array, therfore, we used [] twice. To access the elements of a three dimensional array we need to use [] thrice and so one. Be careful while using multidimensional arrays, as they would add complications to your code. We can also print the whole array with the echo command:

echo $countryCities;

The output would be:
[Saudi Arabia] => Array
[0] => Makkah
[1] => Madina
[UAE] => Array
[0] => Dubai
[1] => Sharjah
[Pakistan] => Array
[0] => Lahore
[1] => Karachi

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