PHP. Predefined Exceptions

Exception

The base class for all exceptions in PHP is Exception. It is used when something goes wrong in the code that should be handled gracefully.

try {
    throw new Exception("Something went wrong!");
} catch (Exception $e) {
    echo "Caught exception: " . $e->getMessage();
}

// Caught exception: Something went wrong!

ErrorException

An ErrorException is thrown when a standard PHP error (like a warning or notice) is converted into an exception. You can set this behavior using set_error_handler().

function errorToException($severity, $message, $file, $line) {
    throw new ErrorException($message, 0, $severity, $file, $line);
}

set_error_handler("errorToException");

try {
    echo $undefinedVar;
} catch (ErrorException $e) {
    echo "ErrorException caught: " . $e->getMessage();
}

// ErrorException caught: Undefined variable $undefinedVar

ClosedGeneratorException

Thrown when you attempt to interact with a closed generator.

function gen() {
    yield 1;
}

$generator = gen();
$generator->next();
$generator->next(); // generator closes

try {
    $generator->send("value"); // invalid on closed generator
} catch (ClosedGeneratorException $e) {
    echo "Caught ClosedGeneratorException: " . $e->getMessage();
}

Error

Error is the base class for all internal PHP errors. Unlike Exception, it represents fatal issues in code execution.

try {
    nonExistingFunction();
} catch (Error $e) {
    echo "Caught Error: " . $e->getMessage();
}

// Caught Error: Call to undefined function nonExistingFunction()

ArgumentCountError

Thrown when a function is called with too few or too many arguments.

function greet($name) {
    return "Hello, $name!";
}

try {
    echo greet(); // missing argument
} catch (ArgumentCountError $e) {
    echo "Caught ArgumentCountError: " . $e->getMessage();
}

// Caught ArgumentCountError: Too few arguments to function greet(), 0 passed

ArithmeticError

Occurs when an invalid arithmetic operation happens.

try {
    $result = intdiv(PHP_INT_MIN, -1); // invalid integer division
} catch (ArithmeticError $e) {
    echo "Caught ArithmeticError: " . $e->getMessage();
}

// Caught ArithmeticError: Division of PHP_INT_MIN by -1 is not an integer

AssertionError

Thrown when an assertion fails (if assertions are enabled).

ini_set('assert.exception', 1);

try {
    assert(false, "Assertion failed!");
} catch (AssertionError $e) {
    echo "Caught AssertionError: " . $e->getMessage();
}

// Caught AssertionError: Assertion failed!

DivisionByZeroError

Thrown when dividing an integer by zero.

try {
    $x = intdiv(10, 0);
} catch (DivisionByZeroError $e) {
    echo "Caught DivisionByZeroError: " . $e->getMessage();
}

// Caught DivisionByZeroError: Division by zero

CompileError

Occurs when the PHP engine encounters a compile-time error. These are rare and usually unrecoverable.

try {
    eval('function test( {'); // invalid syntax at compile time
} catch (CompileError $e) {
    echo "Caught CompileError: " . $e->getMessage();
}

// Caught CompileError: syntax error, unexpected token "{", expecting variable

ParseError

Thrown when eval() encounters a parsing error.

try {
    eval('echo "Missing semicolon"'); // syntax error
} catch (ParseError $e) {
    echo "Caught ParseError: " . $e->getMessage();
}

// Caught ParseError: syntax error, unexpected end of file, expecting "," or ";"

TypeError

Thrown when an argument or return value does not match a type declaration.

function square(int $x): int {
    return $x * $x;
}

try {
    echo square("hello"); // wrong type
} catch (TypeError $e) {
    echo "Caught TypeError: " . $e->getMessage();
}

// Caught TypeError: square(): Argument #1 ($x) must be of type int, string given

ValueError

Introduced in PHP 8, thrown when a function receives an argument of the correct type but with an invalid value.

try {
    $str = substr("hello", -10, -5); // invalid value
} catch (ValueError $e) {
    echo "Caught ValueError: " . $e->getMessage();
}

UnhandledMatchError

Thrown when a match expression does not handle all possible values.

try {
    $x = 5;

    $result = match ($x) {
        1 => "One",
        2 => "Two",
    };
} catch (UnhandledMatchError $e) {
    echo "Caught UnhandledMatchError: " . $e->getMessage();
}

// Caught UnhandledMatchError: Unhandled match case 5

FiberError

Introduced in PHP 8.1, this occurs when there's invalid use of Fibers (lightweight concurrency).

$fiber = new Fiber(function () {
    return "Hello from Fiber!";
});

try {
    $fiber->resume();
    $fiber->resume(); // invalid, already finished
} catch (FiberError $e) {
    echo "Caught FiberError: " . $e->getMessage();
}

// Caught FiberError: Cannot resume a fiber that is not suspended

RequestParseBodyException

Thrown in request_parse_body() when the request body is invalid, according to the Content-Type header.

try {
    throw new RequestParseBodyException("Invalid JSON body");
} catch (RequestParseBodyException $e) {
    echo "Caught RequestParseBodyException: " . $e->getMessage();
}

// Caught RequestParseBodyException: Invalid JSON body

Source: Orkhan Alishov's notes