About the app
Creating drop-down menus can be a pain when there are lots of options. Wouldn't it be nice if we could use a function in PHP to create the menu for us?
That's the whole point of this app.
First, we created a list of gifts and stored them in a motel-like data structure called an 'array.'
A simple array in PHP:
Observe the syntax to create an array in PHP. The 'array' PHP function stores comma-separated elements in each 'index' (room number) of the 'motel.' It is (almost?) universal that the first index is zero rather than one. This is known as 'zero-based indexing'.
<?php
$arr = array("Partridge in a Pear Tree", "Turtle Dove", "French Hen", "Calling Bird", "Gold Ring", "Geese-a-Laying", "Swan-a-Swimming", "Maid-a-Milking", "Lady Dancing", "Lord-a-Leaping", "Piper piping", "Drummer Drumming");
?>
In the example above, the partridge is in room zero, the turtle dove is in room 2, etc.
Look at the drop-down menu of 12 gifts in the form. It was created with a function with only ten lines! To add additional options, we'd only have to add more elements to our array!
The Create Select Menu from Array Function:
Here's the nifty function that creates our drop-down menu:
function createSelectMenuFromArray($name, $arr, $selectedValue){
echo "<select name=\"$name\" id=\"$name\">";
$length = count($arr); //number of elements in $arr
for($ndx = 0; $ndx < $length; $ndx++){
$element = $arr[$ndx];
if($ndx == ($selectedValue - 1)) echo "<option value=\"$ndx\" selected>$element</option>";
else echo "<option value=\"$ndx\">$element</option>";
}
echo "</select>";
}//end function createSelectMenuFromArray
Notice that in PHP, when we create an attribute for a tag like 'name="menu"' we must 'escape' the quotes within PHP using the backslash (\). Why? Because a quote is a programatic character in PHP (it has code-meaning) and the \" routine is a way to make it act like a normal character.
See how we count elements in an array and use that count to construct a for loop that iterates through all elements and places them in 'option's that are echoed into the webpage? That's what is so powerful about PHP: we can automate certain processes with functions, place those functions in utility libraries, then use them whenever we need them.
To pre-select a 'default' value (in this case, it was 'Gold Ring' with array index number 4 (the 5th element, by the way)) we used if-else selection logic to see if control variable $ndx was equal (==, by the way) to $selectedValue. If it was, we included the 'selected' attribute in the option tag. Otherwise that attribute was not included.
In this way, we could customize how the drop-down menu work when first loaded.
12/17/19
