Creating Your First PHP Function
When you create a function, you first need to give it a name, like myCompanyMotto.
It's with this function name that you will be able to call upon your function, so make it easy to type and understand.
The actual syntax for creating a function is pretty self-explanatory, but you can be the judge of that.
First, you must tell PHP that you want to create a function. You do this by typing the keyword function followed
by your function name and some other stuff (which we'll talk about later).
Here is how you would make a function called myCompanyMotto. Note: We still have
to fill in the code for myCompanyMotto.
PHP Code:
<?php
function myCompanyMotto(){
}
?>
Note: Your function name can start with a letter or underscore "_", but not a number!
With a properly formatted function in place, we can now fill in the code that we want our
function to execute. Do you see the curly braces in the above example "{ }"? These braces define
where our function's code goes. The opening curly brace "{" tells php that the function's code is starting and a closing
curly brace "}" tells PHP that our function is done!
We want our function to print out the company motto each time it's called, so that sounds like it's a job for the echo command!
PHP Code:
<?php
function myCompanyMotto(){
echo "We deliver quantity, not quality!<br />";
}
?>
That's it! You have written your first PHP function from scratch! Notice that the code that appears within a function is just the same as any other PHP code.
Using Your PHP Function
Now that you have completed coding your PHP function, it's time to put it through a test run. Belowis a simple PHP script. Let's do two things: add the function code to it and use the function twice.
PHP Code:
<?php echo "Welcome to Tizag.com <br />"; echo "Well, thanks for stopping by! <br />"; echo "and remember... <br />"; ?>
PHP Code with Function:
<?php function myCompanyMotto(){ echo "We deliver quantity, not quality!<br />"; } echo "Welcome to Tizag.com <br />"; myCompanyMotto(); echo "Well, thanks for stopping by! <br />"; echo "and remember... <br />"; myCompanyMotto(); ?>
Display:
Welcome to Tizag.com
We deliver quantity, not quality!
Well, thanks for stopping by!
and remember...
We deliver quantity, not quality!
We deliver quantity, not quality!
Well, thanks for stopping by!
and remember...
We deliver quantity, not quality!
Although this was a simple example, it's important to understand that there
is a lot going on and there are a lot of areas to make errors. When you are creating a function, follow
these simple guidelines:
- Always start your function with the keyword function
- Remember that your function's code must be between the "{" and the "}"
- When you are using your function, be sure you spell the function name correctly
- Don't give up!
PHP Functions - Parameters
Another useful thing about functions is that you can send them information thatthe function can then use. Our first function myCompanyMotto isn't all that
useful because all it does, and ever will do, is print out a single, unchanging string.
However, if we were to use parameters, then we would be able to add some extra functionality!
A parameter appears with the parentheses "( )" and looks just like a normal PHP variable.
Let's create a new function that creates a custom greeting based off of a person's name.
Our parameter will be the person's name and our function will concatenate this
name onto a greeting string. Here's what the code would look like.
PHP Code with Function:
<?php function myGreeting($firstName){ echo "Hello there ". $firstName . "!<br />"; } ?>
When we use our myGreeting function we have to send it a string containing someone's name, otherwise
it will break. When you add parameters, you also add more responsibility to you, the programmer!
Let's call our new function a few times with some common first names.
PHP Code:
<?php
function myGreeting($firstName){
echo "Hello there ". $firstName . "!<br />";
}
myGreeting("Jack");
myGreeting("Ahmed");
myGreeting("Julie");
myGreeting("Charles");
?>
Display:
Hello there Jack!
Hello there Ahmed!
Hello there Julie!
Hello there Charles!
It is also possible to have multiple parameters in a function. To separate multiple parameters
PHP uses a comma ",". Let's modify our function to also include last names.
PHP Code:
<?php function myGreeting($firstName, $lastName){ echo "Hello there ". $firstName ." ". $lastName ."!<br />"; } myGreeting("Jack", "Black"); myGreeting("Ahmed", "Zewail"); myGreeting("Julie", "Roberts"); myGreeting("Charles", "Schwab"); ?>
Display:
Hello there Jack Black!
Hello there Ahmed Zewail!
Hello there Julie Roberts!
Hello there Charles Schwab!
Hello there Ahmed Zewail!
Hello there Julie Roberts!
Hello there Charles Schwab!
PHP Functions - Returning Values
Besides being able to pass functions information, you can also have them return a value.However, a function can only return one thing, although that thing can be any integer, float, array, string, etc. that you choose!
How does it return a value though? Well, when the function is used and finishes executing, it sort of changes from being a function name into being a value. To capture this value you can set a variable equal to the function. Something like:
- $myVar = somefunction();
Let's demonstrate this returning of a value by using a simple function that returns the sum of two integers.
PHP Code:
<?php
function mySum($numX, $numY){
$total = $numX + $numY;
return $total;
}
$myNumber = 0;
echo "Before the function, myNumber = ". $myNumber ."<br />";
$myNumber = mySum(3, 4); // Store the result of mySum in $myNumber
echo "After the function, myNumber = " . $myNumber ."<br />";
?>
Display:
Before the function, myNumber = 0
After the function, myNumber = 7
After the function, myNumber = 7
When we first print out the value of $myNumber it is still set to the original value of 0.
However, when we set $myNumber equal to the function mySum, $myNumber
is set equal to mySum's result. In this case, the result was 3 + 4 = 7, which was successfully
stored into $myNumber and displayed in the second echo statement!
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