How can using incorrect syntax, like missing the $ sign before a variable, lead to errors in PHP code?

Using incorrect syntax, such as missing the $ sign before a variable, can lead to errors in PHP code because PHP requires variables to be prefixed with a $ sign to distinguish them from other elements in the code. This can result in PHP interpreting the variable as a constant or undefined, leading to unexpected behavior or errors in the code. To fix this issue, always ensure that variables are properly declared with the $ sign before their names.

// Incorrect syntax: missing $ sign before variable
name = "John Doe";
echo $name;
```

```php
// Corrected syntax: variable properly declared with $ sign
$name = "John Doe";
echo $name;