🧾 PHP Constants Cheat Sheet (with Examples) — PHP 8.4 Ready

A clean and categorized reference of the most useful constants in PHP.
Includes descriptions and sample outputs for context. Fully valid for PHP 8.3 and safe for PHP 8.4.

🗂 Filesystem & Path Constants

Constant	Description	Example Output
`DIRECTORY_SEPARATOR`	Path separator (`/` on Unix, `\` on Windows)	`/`
`PATH_SEPARATOR`	Include path separator (`:` or `;`)	`:`
`__FILE__`	Full path and filename of the current file	`/var/www/html/index.php`
`__DIR__`	Directory of the current file	`/var/www/html`
`__LINE__`	Line number in the file	`42`

🧠 Magic Constants

Constant	Description	Example Output
`__FUNCTION__`	Current function name	`myFunction`
`__CLASS__`	Current class name	`MyClass`
`__TRAIT__`	Current trait name	`MyTrait`
`__METHOD__`	Current class method	`MyClass::myMethod`
`__NAMESPACE__`	Current namespace	`App\Controllers`

🖥 PHP Environment & System Constants

Constant	Description	Example Output
`PHP_VERSION`	Full PHP version	`8.4.0-dev`
`PHP_MAJOR_VERSION`	Major version	`8`
`PHP_MINOR_VERSION`	Minor version	`4`
`PHP_RELEASE_VERSION`	Patch version	`0`
`PHP_OS`	Operating system name (from compiler)	`Linux`, `WINNT`, `Darwin`
`PHP_OS_FAMILY`	General OS family (portable grouping)	`Linux`, `Windows`, `BSD`, `macOS`
`PHP_SAPI`	Server API type	`cli`
`PHP_EOL`	End-of-line character	`\n`
`PHP_INT_MAX`	Max integer supported	`9223372036854775807`
`PHP_INT_MIN`	Min integer supported	`-9223372036854775808`
`PHP_FLOAT_MAX`	Max float supported	`1.7976931348623E+308`
`PHP_FLOAT_MIN`	Min float supported	`2.2250738585072E-308`

🧾 Error Reporting Constants

Constant	Description	Error Type
`E_ERROR`	Fatal run-time errors	Fatal
`E_WARNING`	Non-fatal run-time warnings	Warning
`E_PARSE`	Compile-time parse errors	Fatal
`E_NOTICE`	Notices about potential issues	Notice
`E_CORE_ERROR`	PHP core fatal errors	Fatal
`E_CORE_WARNING`	PHP core warnings	Warning
`E_COMPILE_ERROR`	Compile-time fatal errors	Fatal
`E_COMPILE_WARNING`	Compile-time warnings	Warning
`E_USER_ERROR`	User-generated fatal error	Fatal
`E_USER_WARNING`	User-generated warning	Warning
`E_USER_NOTICE`	User-generated notice	Notice
`E_STRICT`	Suggests code improvements	Best practice
`E_RECOVERABLE_ERROR`	Catchable fatal error	Fatal (catchable)
`E_DEPRECATED`	Deprecated feature used	Warning
`E_USER_DEPRECATED`	User-generated deprecation notice	Warning
`E_ALL`	All error levels	Aggregate

📁 File Upload Error Constants

Constant	Description	Code
`UPLOAD_ERR_OK`	No error, file uploaded successfully	`0`
`UPLOAD_ERR_INI_SIZE`	File exceeds `upload_max_filesize` in php.ini	`1`
`UPLOAD_ERR_FORM_SIZE`	File exceeds `MAX_FILE_SIZE` in HTML form	`2`
`UPLOAD_ERR_PARTIAL`	File was only partially uploaded	`3`
`UPLOAD_ERR_NO_FILE`	No file was uploaded	`4`
`UPLOAD_ERR_NO_TMP_DIR`	Missing temporary folder	`6`
`UPLOAD_ERR_CANT_WRITE`	Failed to write file to disk	`7`
`UPLOAD_ERR_EXTENSION`	Upload stopped by a PHP extension	`8`

💻 CLI Stream Constants

Constant	Description	Available In
`STDIN`	Standard input stream	CLI only
`STDOUT`	Standard output stream	CLI only
`STDERR`	Standard error stream	CLI only

📌 Tip: These constants are built into PHP — no import or setup needed.
🧠 Valid for PHP 8.3+ and future-proof for PHP 8.4.

MrPunyapal/php_constants_cheatsheet.md