Which of the following is NOT a valid variable name in PHP?$_variable$1_variable$variable$my_variable

To determine which option is NOT a valid variable name in PHP, let's break down the rules for valid variable names in PHP:

1. PHP variable names must start with a dollar sign ($), followed by either a letter (a-z, A-Z) or an underscore (_).
2. After the first character, the name can include letters, numbers (0-9), and underscores.
3. Variable names are case-sensitive.

Now, let's analyze each option provided:

1. $_variable: This starts with a dollar sign followed by an underscore, which is valid.
2. $1_variable: This starts with a dollar sign but then begins with a number (1), which is NOT valid.
3. $variable: This starts with a dollar sign followed by a letter, which is valid.
4. $my_variable: This is also a valid variable name since it starts with a dollar sign and includes letters and an underscore.

Final Answer

$1_variable is NOT a valid variable name in PHP.