Error Identifier: cast.string

Every error reported by PHPStan has an error identifier. Here’s a list of all error identifiers. In PHPStan Pro you can see the error identifier next to each error and filter errors by their identifiers.

Code example #

<?php declare(strict_types = 1);

$value = (string) new stdClass();

Why is it reported? #

The expression being cast to string is of a type that cannot be converted to a string. PHP does not support casting certain types to string unless the class implements the __toString() method. Attempting to cast an object without __toString() to string will result in a fatal error at runtime.

In the example above, stdClass does not implement __toString(), so it cannot be cast to string.

How to fix it #

Implement the __toString() method on the class:

 <?php declare(strict_types = 1);
 
-$value = (string) new stdClass();
+class MyClass
+{
+    public function __toString(): string
+    {
+        return 'my value';
+    }
+}
+
+$value = (string) new MyClass();

Or extract the string value from the object explicitly:

 <?php declare(strict_types = 1);
 
-$value = (string) new stdClass();
+$obj = new stdClass();
+$obj->name = 'hello';
+$value = $obj->name;

How to ignore this error #

You can use the identifier cast.string to ignore this error using a comment:

// @phpstan-ignore cast.string
codeThatProducesTheError();

You can also use only the identifier key to ignore all errors of the same type in your configuration file in the ignoreErrors parameter:

parameters:
	ignoreErrors:
		-
			identifier: cast.string

Rules that report this error #

PHPStan\Rules\Cast\InvalidCastRule [1]

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