Constants

Constants
Magic Constants
These magic constants change their values depending on where they are used.
Name	Description
__CLASS__	The name of the class that the method belongs to, along with and the containing namespace. If it is used in a trait method, gives the value of the class in which the trait is used.
__DIR__	The directory of the current file. If this is used inside an included file, it refers to the included file. This is equivalent to dirname(__FILE__). This directory name does not have a trailing slash unless it is the root directory.
__FILE__	The full path and filename of the current file. If this is used inside an included file, it refers to the included file.
__FUNCTION__	The name of the function containing function. Otherwise, it returns "{closure}" if it is an anonymous function.
__LINE__	The current line number in this file.
__METHOD__	The name of the method that contains the constant.
__NAMESPACE__	The name of the namespace that contains the constant.
__TRAIT__	The name of the trait that the method belongs to, along with and the containing namespace.
<< Class Name >>::class	The name of the class, along with and the containing namespace.
Predefined Constants
These are the constants that are defined as the PHP core, including Zend and SAPI.
Name	Description
PHP_VERSION	This is a string that defines the current version. For example, this is the string "7.4.1-extra" for the PHP version 7.4.1-extra.
PHP_MAJOR_VERSION	This is an integer that defines the current major version. For example, this is the integer 7 for the PHP version 7.4.1-extra.
PHP_MINOR_VERSION	This is an integer that defines the current minor version. For example, this is the integer 4 for the PHP version 7.4.1-extra.
PHP_RELEASE_VERSION	This is an integer that defines the current release version. For example, this is the integer 1 for the PHP version 7.4.1-extra.
PHP_VERSION_ID	This is an integer that defines the current PHP version as an integer. This can be used to compare versions. For example, this is the integer 70401 for the PHP version 7.4.1-extra.
PHP_EXTRA_VERSION	This is a string that defines the current extra version. For example, this is the string "-extra" for the PHP version 7.4.1-extra.
PHP_ZTS	This is an integer value that indicates whether or not the Zend Thread Safety is enabled. The value 0 is equivalent to false and indicates that the current PHP version is not thread safe.
PHP_DEBUG	This is an integer that indicates whether or not PHP debugging is enabled. The value 0 is equivalent to false.
PHP_MAXPATHLEN	This is an integer that indicates the maximum number of characters that are supported for a filename and path.
PHP_OS	This is a string that specifies the operating system for which this version of PHP was built. The string "WINNT" is an example.
PHP_OS_FAMILY	This is a string that specifies the operating system family for which this version of PHP was built. The string "Windows" is an example.
PHP_SAPI	This is a string that specifies the server API for this version of PHP. The string "cgi-fcgi" is an example.
PHP_EOL	This is a string that specifies the end of line character for the currrent platform. The strings "\n" and "\r\n" are examples for Unix and Windows, respectively.
PHP_INT_MAX	An integer that is the largest integer value: 2147483647 or 9223372036854775807 for 32 bit or 64 bit systems, respectively.
PHP_INT_MIN	An integer that is the smallest integer value: -2147483648 or -9223372036854775808 for 32 bit or 64 bit systems, respectively.
PHP_INT_SIZE	The number of bytes used to represent an integer: 4 or 8 bytes for 32 bit or 64 bit systems, respectively.
PHP_FLOAT_DIG	An integer that indicates the number of decimal digits that can be represented via the mantissa of a float value. Typically, this might be 15.
PHP_FLOAT_EPSILON	The smallest float value that can be added to 1 such that the result is a value greater than 1. An example value for this is 2.2204460492503E-16.
PHP_FLOAT_MIN	The smallest positive float value that can be represented. An example value for this is 2.2250738585072E-308.
PHP_FLOAT_MAX	The largest float value that can be represented. An example value for this is 1.7976931348623E+308.
DEFAULT_INCLUDE_PATH	A string that tells the default include path. The string ".;C:\php\pear" is an example.
PEAR_INSTALL_DIR	A string that tells where pear is installed. The string "C:\php\pear" is an example.
PEAR_EXTENSION_DIR	A string that tells where the pear extension is installed. The string "C:\php\ext" is an example.
PHP_EXTENSION_DIR	A string that tells where the PHP extensions are. The string "C:\php\ext" is an example.
PHP_PREFIX	A string that tells the prefix value for PHP paths. The string "C:\php\" is an example.
PHP_BINDIR	A string that tells the bindir value for PHP paths. The string "C:\php\" is an example.
PHP_BINARY	A string that tells where the binary file for PHP is. The string "C:\Program Files\PHP\v7.4\php-cgi.exe" is an example.
PHP_MANDIR	A string that tells the directory where the man pages (instruction pages) were installed.
PHP_LIBDIR	A string that tells the directory where the libraries were installed. The string "C:\php\" is an example.
PHP_DATADIR	A string that tells the directory where the data files were installed. The string "C:\php\" is an example.
PHP_SYSCONFDIR	A string that tells the directory where the system configuration files were installed. The string "C:\php\" is an example.
PHP_LOCALSTATEDIR	A string that tells the directory where the local state files were installed. The string "C:\php\" is an example.
PHP_CONFIG_FILE_PATH	A string that tells the path where the configuation files are to be installed. The string "C:\WINDOWS" is an example.
PHP_CONFIG_FILE_SCAN_DIR	A string that tells the directory where the file scan files were installed.
PHP_SHLIB_SUFFIX	A string that indicates the file extension for libraries. The strings "so" and "dll" are examples for Unix and Windows, respectively.
PHP_FD_SETSIZE	An integer that indicate the maximum number of file descriptors for select system calls. The number 256 is an example.
E_ERROR	The integer value that is reported for a fatal run-time error. The value 1 is an example.
E_WARNING	The integer value that is reported for a run-time warning. The value 2 is an example.
E_PARSE	The integer value that is reported for a compile-time parsing error. The value 4 is an example.
E_NOTICE	The integer value that is reported for a run-time notice. This could be an error or a normal occurance. The value 8 is an example.
E_CORE_ERROR	The integer value that is reported for an initial PHP start-up error that is generated by the core of PHP. The value 16 is an example.
E_CORE_WARNING	The integer value that is reported for an initial PHP start-up warning that is generated by the core of PHP. The value 32 is an example.
E_COMPILE_ERROR	The integer value that is reported for a fatal compile-time error. The value 64 is an example.
E_COMPILE_WARNING	The integer value that is reported for a fatal compile-time warning. The value 128 is an example.
E_USER_ERROR	The integer value that is reported for a user-generated error. It is generated by the trigger_error() function. The value 256 is an example.
E_USER_WARNING	The integer value that is reported for a user-generated warning. It is generated by the trigger_error() function. The value 512 is an example.
E_USER_NOTICE	The integer value that is reported for a user-generated notice. It is generated by the trigger_error() function. The value 1024 is an example.
E_STRICT	The integer value is used to set PHP to strict mode. The value 2048 is an example.
E_RECOVERABLE_ERROR	The integer value is used to indicate a recoverable error. The value 4096 is an example.
E_DEPRECATED	The integer value is used to indicate deprecated PHP features. The value 8192 is an example.
E_USER_DEPRECATED	The integer value is used to indicate user-generated deprecated PHP features. The value 16384 is an example.
E_ALL	The integer value is used to indicate all errors, warnings, and notices. The value 32767 is an example.
__COMPILER_HALT_OFFSET__	An integer used to indicate a compiler halt offset.
true	A boolean value that indicates a true value.
false	A boolean value that indicates a false value.
null	The null value is used to indicate a nonexistent object.
PHP_WINDOWS_EVENT_CTRL_C	An integer that is used to indicate a control + c (copy) event.
PHP_WINDOWS_EVENT_CTRL_BREAK	An integer that is used to indicate a control + break event.