What are common error messages related to unexpected characters in PHP code, and how can they be resolved?

Common error messages related to unexpected characters in PHP code include "Parse error: syntax error, unexpected 'character'" or "unexpected T_STRING". These errors typically occur when there is a syntax error in the code, such as missing or misplaced quotes, brackets, or semicolons. To resolve these issues, carefully review the code for any typos or missing characters, and ensure that all opening and closing brackets, quotes, and semicolons are properly paired.

// Example code with unexpected character issue
echo "Hello World'
```

```php
// Corrected code with missing closing quote
echo "Hello World";