Regex Tester & Validator

Matches function calls to `fopen` or `fwrite` in PHP code by capturing the function name, opening parenthesis, arguments that don't contain a dollar sign (excluding PHP variables), and either a comma or closing parenthesis. This pattern is useful for security analysis, code auditing, or identifying file I/O operations in PHP applications where you want to find hardcoded file operations rather than those using variables. The flags enable case-insensitive and multiline matching across the entire input.