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Editor to share with you what are the reserved words in php, I believe most people do not know much about it, so share this article for your reference, I hope you can learn a lot after reading this article, let's go to know it!

These words have special meanings in PHP. Some of them are like functions, some are like constants. But they are not, they are only part of the language structure. You cannot use any of them as constants, method names, or class names. But you can use them as variable names, but this can lead to confusion.

PHP keyword

And or xor _ _ FILE__ exception (PHP 5)

_ _ LINE__ array () as break case

Class const continue declare default

Die () do echo else elseif

Empty () enddeclare endfor endforeach endif

Endswitch endwhile eval () exit () extends

For foreach function global if

Include include_once isset () list () new

Print require require_once return static

Switch unset () use var while

_ _ FUNCTION__ CLASS__ METHOD__ final (PHP 5) php_user_filter (PHP 5)

Interface (PHP 5) implements (PHP 5) extends public (PHP 5) private (PHP 5)

Protected (PHP 5) abstract (PHP 5) clone (PHP 5) try (PHP 5) catch (PHP 5)

Throw (PHP 5) cfunction (PHP 4 only) this (PHP 5 only)

Predefined class

Section lists the standard predefined classes. The various extension libraries define other classes, which are described in their respective reference documents.

Standard class

These classes are defined by standard functions built into PHP.

Directory

Created by dir ().

StdClass

_ _ PHP_Incomplete_Class

Predefined classes since PHP 5

These additional predefined classes were introduced by PHP 5.0.0.

Exception

Php_user_filter

Closure

A predefined final class Closure is introduced into PHP5.3.0, which can be used to implement anonymous functions.

The constructor of this class forbids manual creation of objects of this class (which results in an E_RECOVERABLE_ERROR error). This class also has a _ _ invoke method to make magic calls.

Special class

The following tags cannot be used as class names because they have a special purpose.

Self

Parent

Predefined constant

Kernel predefined constant

These constants are defined in the kernel of PHP. It contains PHP, Zend engine, and SAPI modules.

PHP_VERSION (string)

PHP_OS (string)

PHP_SAPI (string)

Available since PHP 4.2.0. See php_sapi_name ().

PHP_EOL (string)

Available since PHP 4.3.10 and PHP 5.0.2

PHP_INT_MAX (integer)

Available since PHP 4.4.0 and PHP 5.0.5

PHP_INT_SIZE (integer)

Available since PHP 4.4.0 and PHP 5.0.5

DEFAULT_INCLUDE_PATH (string)

PEAR_INSTALL_DIR (string)

PEAR_EXTENSION_DIR (string)

PHP_EXTENSION_DIR (string)

PHP_PREFIX (string)

Available since PHP 4.3.0

PHP_BINDIR (string)

PHP_LIBDIR (string)

PHP_DATADIR (string)

PHP_SYSCONFDIR (string)

PHP_LOCALSTATEDIR (string)

PHP_CONFIG_FILE_PATH (string)

PHP_CONFIG_FILE_SCAN_DIR (string)

PHP_SHLIB_SUFFIX (string)

Available since PHP 4.3.0

PHP_OUTPUT_HANDLER_START (integer)

PHP_OUTPUT_HANDLER_CONT (integer)

PHP_OUTPUT_HANDLER_END (integer)

E_ERROR (integer)

E_WARNING (integer)

E_PARSE (integer)

E_NOTICE (integer)

E_CORE_ERROR (integer)

E_CORE_WARNING (integer)

E_COMPILE_ERROR (integer)

E_COMPILE_WARNING (integer)

E_USER_ERROR (integer)

E_USER_WARNING (integer)

E_USER_NOTICE (integer)

E_ALL (integer)

E_STRICT (integer)

Valid from PHP 5.0.0

_ _ COMPILER_HALT_OFFSET__ (integer)

Valid as of PHP 5.1.0

See Magic constant.

Standard predefined constant

These constants are defined by default by PHP.

EXTR_OVERWRITE (integer)

EXTR_SKIP (integer)

EXTR_PREFIX_SAME (integer)

EXTR_PREFIX_ALL (integer)

EXTR_PREFIX_INVALID (integer)

EXTR_PREFIX_IF_EXISTS (integer)

EXTR_IF_EXISTS (integer)

SORT_ASC (integer)

SORT_DESC (integer)

SORT_REGULAR (integer)

SORT_NUMERIC (integer)

SORT_STRING (integer)

CASE_LOWER (integer)

CASE_UPPER (integer)

COUNT_NORMAL (integer)

COUNT_RECURSIVE (integer)

ASSERT_ACTIVE (integer)

ASSERT_CALLBACK (integer)

ASSERT_BAIL (integer)

ASSERT_WARNING (integer)

ASSERT_QUIET_EVAL (integer)

CONNECTION_ABORTED (integer)

CONNECTION_NORMAL (integer)

CONNECTION_TIMEOUT (integer)

INI_USER (integer)

INI_PERDIR (integer)

INI_SYSTEM (integer)

INI_ALL (integer)

Masking E (float)

M_LOG2E (float)

M_LOG10E (float)

M_LN2 (float)

M_LN10 (float)

M_PI (float)

M_PI_2 (float)

M_PI_4 (float)

M_1_PI (float)

M_2_PI (float)

M_2_SQRTPI (float)

M_SQRT2 (float)

M_SQRT1_2 (float)

CRYPT_SALT_LENGTH (integer)

CRYPT_STD_DES (integer)

CRYPT_EXT_DES (integer)

CRYPT_MD5 (integer)

CRYPT_BLOWFISH (integer)

DIRECTORY_SEPARATOR (string)

SEEK_SET (integer)

SEEK_CUR (integer)

SEEK_END (integer)

LOCK_SH (integer)

LOCK_EX (integer)

LOCK_UN (integer)

LOCK_NB (integer)

HTML_SPECIALCHARS (integer)

HTML_ENTITIES (integer)

ENT_COMPAT (integer)

ENT_QUOTES (integer)

ENT_NOQUOTES (integer)

INFO_GENERAL (integer)

INFO_CREDITS (integer)

INFO_CONFIGURATION (integer)

INFO_MODULES (integer)

INFO_ENVIRONMENT (integer)

INFO_VARIABLES (integer)

INFO_LICENSE (integer)

INFO_ALL (integer)

CREDITS_GROUP (integer)

CREDITS_GENERAL (integer)

CREDITS_SAPI (integer)

CREDITS_MODULES (integer)

CREDITS_DOCS (integer)

CREDITS_FULLPAGE (integer)

CREDITS_QA (integer)

CREDITS_ALL (integer)

STR_PAD_LEFT (integer)

STR_PAD_RIGHT (integer)

STR_PAD_BOTH (integer)

PATHINFO_DIRNAME (integer)

PATHINFO_BASENAME (integer)

PATHINFO_EXTENSION (integer)

PATH_SEPARATOR (string)

CHAR_MAX (integer)

LC_CTYPE (integer)

LC_NUMERIC (integer)

LC_TIME (integer)

LC_COLLATE (integer)

LC_MONETARY (integer)

LC_ALL (integer)

LC_MESSAGES (integer)

ABDAY_1 (integer)

ABDAY_2 (integer)

ABDAY_3 (integer)

ABDAY_4 (integer)

ABDAY_5 (integer)

ABDAY_6 (integer)

ABDAY_7 (integer)

DAY_1 (integer)

DAY_2 (integer)

DAY_3 (integer)

DAY_4 (integer)

DAY_5 (integer)

DAY_6 (integer)

DAY_7 (integer)

ABMON_1 (integer)

ABMON_2 (integer)

ABMON_3 (integer)

ABMON_4 (integer)

ABMON_5 (integer)

ABMON_6 (integer)

ABMON_7 (integer)

ABMON_8 (integer)

ABMON_9 (integer)

ABMON_10 (integer)

ABMON_11 (integer)

ABMON_12 (integer)

MON_1 (integer)

MON_2 (integer)

MON_3 (integer)

MON_4 (integer)

MON_5 (integer)

MON_6 (integer)

MON_7 (integer)

MON_8 (integer)

MON_9 (integer)

MON_10 (integer)

MON_11 (integer)

MON_12 (integer)

AM_STR (integer)

PM_STR (integer)

D_T_FMT (integer)

D_FMT (integer)

T_FMT (integer)

T_FMT_AMPM (integer)

ERA (integer)

ERA_YEAR (integer)

ERA_D_T_FMT (integer)

ERA_D_FMT (integer)

ERA_T_FMT (integer)

ALT_DIGITS (integer)

INT_CURR_SYMBOL (integer)

CURRENCY_SYMBOL (integer)

CRNCYSTR (integer)

MON_DECIMAL_POINT (integer)

MON_THOUSANDS_SEP (integer)

MON_GROUPING (integer)

POSITIVE_SIGN (integer)

NEGATIVE_SIGN (integer)

INT_FRAC_DIGITS (integer)

FRAC_DIGITS (integer)

P_CS_PRECEDES (integer)

P_SEP_BY_SPACE (integer)

N_CS_PRECEDES (integer)

N_SEP_BY_SPACE (integer)

P_SIGN_POSN (integer)

N_SIGN_POSN (integer)

DECIMAL_POINT (integer)

RADIXCHAR (integer)

THOUSANDS_SEP (integer)

THOUSEP (integer)

GROUPING (integer)

YESEXPR (integer)

NOEXPR (integer)

YESSTR (integer)

NOSTR (integer)

CODESET (integer)

LOG_EMERG (integer)

LOG_ALERT (integer)

LOG_CRIT (integer)

LOG_ERR (integer)

LOG_WARNING (integer)

LOG_NOTICE (integer)

LOG_INFO (integer)

LOG_DEBUG (integer)

LOG_KERN (integer)

LOG_USER (integer)

LOG_MAIL (integer)

LOG_DAEMON (integer)

LOG_AUTH (integer)

LOG_SYSLOG (integer)

LOG_LPR (integer)

LOG_NEWS (integer)

LOG_UUCP (integer)

LOG_CRON (integer)

LOG_AUTHPRIV (integer)

LOG_LOCAL0 (integer)

LOG_LOCAL1 (integer)

LOG_LOCAL2 (integer)

LOG_LOCAL3 (integer)

LOG_LOCAL4 (integer)

LOG_LOCAL5 (integer)

LOG_LOCAL6 (integer)

LOG_LOCAL7 (integer)

LOG_PID (integer)

LOG_CONS (integer)

LOG_ODELAY (integer)

LOG_NDELAY (integer)

LOG_NOWAIT (integer)

LOG_PERROR (integer)

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