From PHP 5.6 onwards, it is possible to define a constant as a scalar expression, and it is also possible to define an array constant. A constant can only be defined using a define() function and not by any simple assignment.
PHP: echoing a constant with a variable name. These special constants are case-insensitive and are as follows − PHP allows you to use dynamic variable names, called variable variables.
It is considered best practice to define constants using only upper-case names.
But your class constant would be accessible from any object instance as well. This means that the following will not work:
Think of a variable as a glass containing water. A constant is a variable with a value that cannot be changed by the script. Here're some important things to know about variables: In PHP, a variable does not need to be declared before adding a value to it.
In other words, once you have defined one, its value is set for the remainder of the program and cannot be altered. You can define a class constant in php. Variable values can change over the course of a script. This goes for any of the string formats in PHP, including heredoc.
For example, the value of __LINE__ depends on the line that it's used on in your script. constant() is an alternative way to get hold of a constant, but a function call can't be put into a string without concatenation either. constant() always behaves as if it is called from the global namespace. Manual on constants in PHP In my situation the isSpeaking and RecipientRoles variables are such that, if isSpeaking is 0, then RecipientRole will be 1 or 0.
A variable is a name given to a memory location that stores data at runtime. The constant value is immutable.
PHP 7 Constant. Constants are defined using PHP's define( ) function, which accepts two arguments: The name of the constant, and its value. Active 3 years, 10 months ago. With Strings, there is no way for PHP to tell string data apart from constant identifiers. 3.
Yes, You can define an array as constant. Use Constants for values that remain fixed and referenced multiple times. Variables are used to store data, like string of text, numbers, etc. However, as of But your class constant would be accessible from any object instance as well. For example, it can be started with a letter or underscore only.
There is no need to use dollar sign($) before constants during assignment but while declaring variables we use a dollar sign. I.e. The general syntax for defining constant is given below: define (“ConstantName” ,value); Example: define (“PI”, 3.14); However it is not mandatory to write constants in upper case, but generally programmer prefer to write them in upper case to distinguish them from variables.
Name of constants must follow the same rules as variable names, which means a valid constant name must starts with a letter or underscore, followed by any number of letters, numbers or underscores with one exception: the $ prefix is not required for constant names. As of PHP 5.4.6 constant() pays no attention to any namespace aliases that might be defined in the file in which it's used.
That is, one variable contains the name of another variable. Constants vs Variables.
Viewed 20k times 14. You can name a variable with the value stored in another variable. PHP constants follow the same PHP variable rules. Note: Unlike variables, constants are automatically global throughout the script. PHP Variable. Constant, Variable, Data Type Operator: Constant: Constant refers to fixed value that does not change the value during the execution of program. The scope of a variable determines its visibility.
A constant, once defined can never be undefined but a variable can be easily undefined.
In PHP you can define constant using define function. Therefore, such a value must be assigned at the same time that the constant is created.