Which of the following is not valid PHP code?
- $_10
- ${"MyVar"}
- &$something
- $10_somethings
In PHP, variable names must start with a letter or underscore, followed by letters, numbers, or underscores. '$10_somethings' starts with a number, which is invalid syntax. '$_10' is valid. '${...}' and '&$var' are valid syntax (variable variables and references).
To answer this question, let's go through each option and determine if it is valid PHP code:
Option A) $_10 - This option is valid PHP code. Variable names in PHP can start with a letter or an underscore, followed by any combination of letters, numbers, or underscores.
Option B) ${"MyVar"} - This option is valid PHP code. It demonstrates the use of variable variables in PHP, where the variable name is constructed by using the value of another variable.
Option C) &$something - This option is valid PHP code. It demonstrates the use of a reference variable in PHP, denoted by the ampersand symbol (&).
Option D) $10_somethings - This option is not valid PHP code. Variable names in PHP cannot start with a number. They must start with a letter or an underscore.
Therefore, the correct answer is D) $10_somethings. This option is not valid PHP code because it violates the naming conventions for variables in PHP.