[Solved] Which variable name is invalid in PHP and why?$user_name$UserName$userName1$user-name — Ans: $user-name because hyphens are not allowed | PHP

PHP - Variables and Data Types

Which variable name is invalid in PHP and why?

$user_name
$UserName
$userName1
$user-name

A$UserName because uppercase letters are not allowed

B$user_name because underscores are not allowed

C$userName1 because numbers are not allowed

D$user-name because hyphens are not allowed

Step-by-Step Solution

Solution:

Step 1: Review allowed characters in PHP variable names
Letters, numbers, and underscores are allowed; hyphens are not.
Step 2: Check each variable
$user-name contains a hyphen, which is invalid. Others are valid.
Final Answer:
$user-name is invalid because hyphens are not allowed. -> Option D
Quick Check:
Hyphens not allowed in variable names = B [OK]

Quick Trick: Hyphens break variable names; use underscores instead [OK]

Common Mistakes:

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