PHP constants

A constant is an identifier (name) for a simple value. As the name suggests, that value cannot change during the execution of the script Constants are case-sensitive. By convention, constant identifiers are always uppercase.

  • Constants variable are automatically global and can be used across the entire script.
  • A valid constant variable name starts with a letter or underscore



To create a constant variable , use the define() function.


// Valid constant names
define("FOO",     "something");
define("FOO2",    "something else");
define("FOO_BAR", "something more");

// Invalid constant names
define("2FOO",    "something");


identifierThis parameter specifies the name of the constant
valueThis parameter specifies the value of the constant
case-insensitiveThis parameter contain bool value the constant name should be case-insensitive. Default is false

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