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InvalidArgumentException in PHP: contract violations, bad config, and malformed input across Symfony, Guzzle, Laravel, and Composer

InvalidArgumentException (\InvalidArgumentException) is the error major PHP libraries throw when a caller breaks a contract — passing a value of the wrong type, a malformed DSN or URL, a misconfigured service tag, an unsupported cURL option, or a missing interface method. You meet it the moment your code hands the library something it cannot use, before any real work begins. This article explains the mechanism behind the family across Symfony, Guzzle, Laravel, and Composer, the recurring shapes it takes, and the cross-library fixes that resolve the bulk of cases.

Distilled from 367 documented records across 4 repositories.

Background

\InvalidArgumentException is PHP's built-in signal that an operation received an argument it cannot accept. It extends \LogicException, which marks it as a programmer error rather than an environmental one: the caller violated a precondition, and the library refuses to proceed. Across the four libraries surveyed here it is thrown early — before a network call, before a database write, before the container finishes compiling — so the stack trace points back at the call site that handed in the bad value rather than at some later, confused failure. The discipline that resolves most cases is reading the message against the value actually being passed, then correcting the call rather than retrying it.

From the caller's side the error is usually self-explanatory once read carefully. The message almost always names the offending value and the expected shape. Guzzle prints the option path and the expected type ('expected float'); Symfony lists the accepted cache.pool tag attributes and the offending one; the Redis DSN validator says which parameter must be a number; Laravel's query builder lists the three acceptable subquery shapes. Because the throw happens before the operation proceeds, the fix lives in the calling code or the configuration, not in retries, fallbacks, or environment changes.

The family takes different shapes in each library. In Symfony it dominates the container and console layer — cache.pool tag typos, firewall-listener classes that cannot be reflected, Twig template names missing the namespace slash, EntityUserProvider missing both a property and a UserLoaderInterface, the TemplatedEmail context reserving the 'email' key. These fire at container compile time, so the application never boots until the definition is corrected. In Guzzle it guards the request-option contract: cURL options that Guzzle itself manages (with a named replacement) or that fall outside its allow-list, request options whose value has the wrong type, and proxy URLs that fail RFC 3986 parsing. In Laravel it polices schema introspection (three-part table references, missing columns), migration class-name collisions, and subquery argument shapes. In Composer it covers unknown installer types, missing installed-state records, and a defensive canary in JsonManipulator that explicitly asks the user to file an upstream bug.

One wrinkle worth flagging: not every record in the family is a pure programmer error. Symfony's RedisAdapter wraps connectivity and authentication failures — connection refused, NOAUTH, SELECT out of range, TLS handshake — under \InvalidArgumentException as well, embedding the low-level Redis error in the message. This is library-specific packaging; the same conditions would surface as \RuntimeException or \RedisException elsewhere. When the message reads 'Redis connection failed', the diagnosis shifts from contract violation to environment check, and the embedded {error} text names the actual cause.

Common causes

What usually fixes it

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Documented occurrences

…and 347 more across the corpus — use search.

Honest provenance: generated on 2026-08-12 from AI-assisted analysis of the linked records. See how records are made.