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How does this function work? A basic php question


bcb
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Hi, Im learning php, but Im a bit confused on this basic problem.

 

I have the following code:

 

<?php

include "tax.php";

$price = 95;

echo "Price before tax: $price <br>";

echo "Price after tax: ";

echo add_tax ($price);

?>

 

 

Which uses the function below

 

<?php

function add_tax ($amount) {

    $total = $amount * 1.09;

    return $total;

}

?>

 

When I execute the code I can see that it does work, but I do not understand why this part works!

 

echo add_tax ($price); 

 

There is no multiplier symbol here, so is the function performed on the ($price) variable simply because of where it is located on this line of code?  Thanks

 

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Your $price variable is being "passed" to the function as an argument.

 

So basically, when you call the function you give it the price to add tax to.

 

Another example would be something like

 

 

function test($var1, $var2){return $var1." ".$var2;}

 

 

That is a simple function that would concatenate two strings together with a space in the middle... so this function is looking for two arguments and would be called like

 

echo test("Hello", "world");

 

Which would echo: Hello world

 

HTH

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The real source to this is return

 

When you return something within a function, you can call that function as if it were a variable.

If your add_tax function had just simply multiplied your argument and exited, you wouldn't have got anything; an error at the least.

 

Using MathewJ's example..as an example, you can see that when test is called it will return a string with the two arguments concatenated

echo test("this and", "that");

would yield: this and that.

 

 

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This is about the most simple way I can think to explain this.

 

<?php
function add_tax ($amount) {
     $total = $amount * 1.09;
     return $total;
}
?>

 

Given the example you provided above.

$total = $amount * 1.09

Lets say the $amount = 7

$total = 7 * 1.09

 

$total now = 7.63

 

return $total

 

return when used in a function like the above poster stated makes the function = what was returned.

 

So now add_tax (7) is equal to 7.63

 

Here is a another way you could use that function.

 

$num = add_tax(7);
$num2 = add_tax(2);

$total = $num * $num2;

echo add_tax($total);

 

The above is just a useless example, but it illustrates a bit more on how it works.

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