Naming conventions used by developers in PHP

Coding conventions are a crucial aspect of maintaining excellent code quality. In this Answer, you will learn the conventions of naming a variable, class, function, and constant and importing a file/library/package in PHP.

Naming variables, functions, iterators, and exceptions

Most PHP developers write variables, functions, iterators, and exception instance names in lowerCamelCase. In addition, their name should be self-explanatory and concise.

Note: A concise name is neither too lengthy nor too short; nonetheless, if a longer name better represents the variable, we choose the longer one.

In lowerCamelCase, the first letter of the first word in a variable name is written in lower case. If the variable name consists of multiple words, all words other than the first word begin with a capital letter.

Example: Naming variables

<?PHP
    /*
      Good variable, function, iterator and exception
      instance names are written in  
      lowerCamelCase, are concise and descriptive
    */
    function sumElementsOfIterable(iterable $myIterable){
        $sum = 0;
        try{
            foreach($myIterable as $element){
                $sum += $element;
            }
        }catch(Exception $objException){
            print($objException);
        }
        return $sum;
    }
    echo sumElementsOfIterable([2, 4, 6, 8]);
?>

Naming classes and interfaces

Class and interface names are always written in UpperCamelCase and are nouns; they should never be adjectives but the interface should end with the "Interface" suffix.

Note: In UpperCamelCase, each word in the variable name begins with a capital letter.

Example: Naming class and interface

<?PHP
    //Good class names are in UpperCamelCase and are nouns
    class ElectricEngine
    {
        // Class details
    }
    /*
      Good Interface names are written in UpperCamelCase
      and end with the Interface suffix
    */
    interface CalculatorInterface{
        // Interface details
    }
?>
PHP class and interface naming convention

Naming constants

Constants' names are always written in the UPPER case and multiple words in one name are usually separated by an underscore.

Example: Naming constants

<?PHP
    /*
      Good constants names are written in UPPER case
      and multiple words within a single name 
      are separated with an underscore
    */
    define("ACCOUNT_DEFICIT", 50);
    define("MONTHLY_PROFIT", null);
    define("EMPLOYEES_HIRED", true);
    echo ACCOUNT_DEFICIT;
?>

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