Language cheatsheet

PHP 8 Cheatsheet

The php command line and the modern PHP 8 syntax you use every day: types, enums, match, PDO and more.

Command line

Check the PHP version — Print the version and build details.
Start a development server — Serve the current folder at http://localhost:8000. For development only.
Serve a public folder with a router script — Serve a document root, sending unknown paths to a front controller.
Run a script — Run a PHP file from the command line.
Run a one-line command — Run PHP code without a file.
Check a file for syntax errors — Check syntax without running the file.
List loaded extensions — Show compiled-in extensions such as pdo_mysql and mbstring.
Find the php.ini file — Show which configuration files are loaded.
Read a configuration value — Print the value of a single configuration setting.
Open the interactive shell — Start an interactive prompt. Exit with Ctrl+D.

Turn on strict typing — Put this on the first line of a file so scalar type declarations aren't silently converted.
Declare types — Type parameters and return values. ?string means string or null.
Use union types — Accept more than one type for a parameter.
Call with named arguments — Name arguments to skip optional ones and make calls readable.
Write an arrow function — A short closure that captures outer variables automatically.
Declare properties in the constructor — Define and assign properties from constructor parameters.
Define an enum — A fixed set of named values, optionally backed by strings or integers.
Use match instead of switch — Match with strict comparison. It returns a value and throws if nothing matches.
Call methods on possible nulls — Short-circuit to null instead of an error.
Provide a default — Use a default when a value is null or missing.

Search in strings — Check the start, end or contents of a string.
Insert variables in strings — Use double quotes or curly braces for expressions.
Transform and filter arrays — Map and filter, then reindex the result.
Extract a column — Pull one field from each row.
Sort with a comparison — Sort an array by a field using the spaceship operator.
Merge arrays — Combine arrays with the spread operator.
Check keys and values — Test whether a key or value exists.
Encode and decode JSON — Convert to and from JSON, throwing exceptions on errors.

Connect with PDO — Connect to MySQL with exceptions on errors. Use real credentials from the environment.
Run a prepared statement — Pass values separately from the SQL, which prevents SQL injection.
Hash a password — Hash passwords with a strong algorithm and a built-in salt. Never store plain text.
Check a password — Compare a password with a stored hash.
Escape output — Escape user-provided values before printing them in HTML, to prevent cross-site scripting.
Validate input — Check that a value is a valid email address.
Start a session — Call it before any output.
Redirect — Send a redirect and stop the script.
Handle exceptions — Catch specific exceptions and always run cleanup in finally.
Use namespaces and autoloading — Declare a namespace, then load classes through Composer's autoloader.

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