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Naming Conventions

Naming Conventions

In this lesson we will look at the naming conventions used in PHP.

Variables

Variables should contain only lowercase letters, use underscore separators and be reasonably named to indicate their purpose and contents. Very short, non-word variables should only be used as iterators in for() loops.

Example: Correct

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//Right
for ($j = 0; $j < 10; $j++)
$str
$buffer
$group_id
$last_city
$first_name = “John”; 
$last_name = “Doe”;

Example: Incorrect

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//Wrong
$n1 = “John”; 
$n2 = “Doe”; 
$my_name = “John Doe”; 
$my_var = “John Doe”; 
$j = 'foo';             // single letter variables should only be used in for() loops
$Str                    // contains uppercase letters
$bufferedText           // uses CamelCasing, and could be shortened without losing semantic meaning
$groupid                // multiple words, needs underscore separator
$name_of_last_city_used // too long

So can you guess what’s wrong with $n1, $n2, $my_name and $my_var ? One word – “Ambiguity”. Ambiguous names are the biggest reason for unreadable and ugly code. So what is “Ambiguity”? It’s simply naming a variable in a way so that you can’t guess what exactly it stores. Consider for example following snippet:

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$i = “Apple iPhone 6S (32GB, Rose Gold)”; 
$p = “749.00”;
$t = “749.00”;

Can you guess in the above code, what is $t? No? Okay, let’s try the following code:

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$item = “Apple iPhone 6S (32GB, Rose Gold)”; 
$price = “749.00”;
$total = “749.00”;

Can you guess now? Exactly! This is how you differentiate ambiguous variables from absolute variables. Obviously the latter approach is better because it is definitive.

Constants

Constants follow the same guidelines as do variables, except constants, should always be fully uppercase. Always use CodeIgniter constants when appropriate, i.e. SLASH, LD, RD, PATH_CACHE, etc.

Example : Incorrect

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myConstant      // missing underscore separator and not fully uppercase
N               // no single-letter constants
S_C_VER         // not descriptive
$str = str_replace('{foo}', 'bar', $str);       // should use LD and RD constants

Example : Correct

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MY_CONSTANT
NEWLINE
SUPER_CLASS_VERSION
$str = str_replace(LD.'foo'.RD, 'bar', $str);

TRUE, FALSE, and NULL

TRUE, FALSE, and NULL keywords should always be fully uppercase.

Example : Incorrect

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if ($foo == true)
$bar = false;
function foo($bar = null)

Example : Correct

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if ($foo == TRUE)
$bar = FALSE;
function foo($bar = NULL)

Functions

There are two functions majorly used:

  • lowercase with underscore separators

  • camelcase

Example

Consider the following two examples:

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function get_name(){
  // Do something
}
function getName(){
  // Do something
}

So which one is best – none, both are equally good!

Always keep in mind that a function should always start with a “Verb” which defines what that function is trying to do in conjunction with the name of the “Entity” being affected by this function.

Example: Incorrect

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databaseConnection() // Wrong
namesList() // Wrong

Example: Correct

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getName() // Right
listNames() // Right
sendEmail() // Right
deleteUserById($id) // Right
connectToDatabase() // Right
prepareOutput() // Right

Class Methods

Class names should always start with an uppercase letter. Multiple words should be separated with an underscore, and not CamelCased.

Example: Incorrect

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class superclass
class SuperClass

Example: Correct

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class Super_class

Class methods should be entirely lowercased and named to clearly indicate their function, preferably including a verb. Try to avoid overly long and verbose names. Multiple words should be separated with an underscore.