PHP Keywords In English

PHP Keywords

In PHP, keywords are predefined words that have specific meanings and purposes within the language. You cannot use these keywords as variable names, constants, class names, traits, namespaces, etc., because it can create conflicts between your defined names and the actual PHP keywords, leading to errors.

Example of Using a PHP Keyword Incorrectly

<?php         
   class ECHO {
       function __construct() {
           echo 'Hello Constructor';
       }
   } 
   // Create a new object of the class
   new ECHO(); 
?> 

Output:

Parse error: syntax error, unexpected 'ECHO' (T_ECHO), expecting identifier (T_STRING) in C:\xampp\htdocs\test\test.php on line 2

In this example, we tried to create a class named ECHO, which is not allowed because echo is a PHP keyword used to print values. Using keywords in this way will cause errors.

Best Practices

When working on a project, ensure that your variables, constants, namespaces, class names, and traits are meaningful and do not conflict with PHP’s predefined keywords. This practice enhances code readability and helps with error handling.

List of PHP Keywords and Their Uses

Keyword Name	Uses
abstract	To define an abstract class
echo / echo()	To print the value assigned in a variable
print / print()	To print the formatted value assigned in a variable
array()	To define an array
and	Used as a logical operator
as	Works with foreach loops
break	To break the structure of the loop (for loop or while loop)
case	Works with switch
catch	Handles errors
class	Defines a class
clone	Makes a clone of an object
const	Defines a constant variable in a class
continue	Skips the current iteration of the loop
die	Exits the script execution; equivalent to exit
exit	Exits the script execution; equivalent to die
do	Works with while loops; executes the script, then checks the condition
if	Executes if the given condition is true
else	Works with the if statement; executes if the condition is not met
elseif	Works with if; executes if the previous condition is not met
empty	Checks if a variable has a value or not
endif	Ends the if-else loop
foreach	Iterates through array variables
endforeach	Ends the foreach loop
for	Iterates the loop of given instructions
endswitch	Ends the switch loop
endwhile	Ends the while loop
extends	Inherits a class
final	Defines a final method, preventing child classes from overriding it
finally	Works with try; the finally block runs every time
function	Defines a function
global	Defines a global variable
goto	Jumps to another section of the program
implements	Indicates that a class implements an interface
include	Includes another file in the current file
include_once	Includes a file only once
interface	Defines an interface
instanceof	Checks if a variable is an instance of a class
isset()	Checks whether a variable is defined or not
namespace	Defines a namespace
new	Creates an object of a class
or	Logical operator
private	Defines private variables or functions in a class
protected	Defines protected variables or functions in a class
public	Defines public variables or functions in a class
require	Includes a file and produces a fatal error if the file does not exist
require_once	Includes a file only once; produces a fatal error if the file does not exist
static	Defines static properties in a class
switch	Starts a switch loop
trait	Defines a trait
try	Handles exceptions
unset()	Unsets a given variable
var	Defines a variable with public visibility in a class
while	Starts a while loop
LINE	Current line number
FILE	Returns the full file path with the file name
DIR	Returns the directory of the file
FUNCTION	Returns the function name or {closure} for anonymous functions
CLASS	Returns the class name
TRAIT	Returns the trait name, which may include a namespace
METHOD	Returns the method name
NAMESPACE	Returns the namespace name

Magic Constants in PHP

PHP provides some magic constants that return values depending on where they are used within the code. These constants can be helpful for debugging and understanding the flow of your script.

Understanding keywords and avoiding their misuse is crucial for writing clean and error-free PHP code.