The real power of PHP comes from its functions.
In PHP, more than 700 built-in functions are provided.
PHP Functions
In this tutorial, we'll show you how to create your own functions.
Creating PHP Functions
A function is a block of code that can be executed whenever needed.
Creating PHP functions:
All functions are named using the keyword "function()" to start
the function - the name of the function should hint at its functionality. Function names start with a letter or underscore.
Add "{" - the part after the opening curly brace is the function's code.
Inserting function code
adds a "}" - the function ends with a closing curly brace.
Example of
a simple function that prints my name when called:
<html>
<body>
<?php
function writeMyName(){
echo "David Yang";
}
writeMyName();
?>
</body>
</html>
Using the PHP function
Now, we are going to use this function in the PHP script:
<?php
function writeMyName(){
echo "David Yang";
}
echo "Hello world!";
echo "My name is ";
writeMyName();
echo ".That's right, ";
writeMyName();
echo "is my name.";
?＞
Output of the above code:
Hello world!
My name is David Yang.
That's right, David Yang is my name.
PHP Function - Adding Parameters
Our first function is a very simple one. It can only output a static string.
By being able to add parameters, we add more functionality to the function. A parameter is like a variable.
You may have noticed that there are parentheses after the function name, such as writeMyName(). Parameters are specified in parentheses.
Example 1
The following example outputs different names but the same last name:
<?php
function writeMyName($fname){
echo $fname . "Yang.";
}
echo "My name is ";
writeMyName("David");
echo "My name is ";
writeMyName("Mike");
echo "My name is ";
writeMyName("John");
?＞
Output of the above code:
My name is David Yang.
My name is Mike Yang.
My name is John Yang.
The function below
in Example 2
has two parameters:<?php
function writeMyName($fname,$punctuation){
echo $fname . " Yang" . $punctuation . "";
}
echo "My name is ";
writeMyName("David",".");
echo "My name is ";
writeMyName("Mike","!");
echo "My name is ";
writeMyName("John","...");
?＞
Output of the above code:
My name is David Yang.
My name is Mike Yang!
My name is John Yang...
PHP Functions - Return Value
Functions can also be used to return values.
Example
＜?php
function add($x,$y){
$total = $x + $y;
return $total;
}
echo "1 + 16 = " . add(1,16);
? >
Output of the above code:
1 + 16 = 17