Variable As String

ID

php.variable_as_string

Severity

low

Remediation Complexity

medium

Remediation Risk

low

Remediation Effort

medium

Resource

Code Smell

Language

Php

Tags

code_smell, strings

Description

Reports two pointless ways of turning a single value into a string: concatenating it with an empty string literal ('' . $x or $x . '') and wrapping a single variable in a double-quoted interpolated string ("$x"). Both produce the value already stringified, with no surrounding text or other operand.

Rationale

'' . $x and "$x" both coerce $x to a string, exactly as (string) $x does, but they hide that intent behind a concatenation or an interpolation and add an unnecessary allocation. The cast form states plainly that a string conversion is happening, reads better in code review, and avoids the small runtime overhead of building a temporary string. A concatenation with a non-empty literal ('id-' . $x) or an interpolation with surrounding text or a second variable ("value: $x", "$x$y") is a real string build and is left alone.

<?php
$a = '' . $x;        // FLAW - empty-string concatenation to stringify
$b = $x . '';        // FLAW - same idiom, other order
$c = "$x";           // FLAW - single interpolated variable as whole string
$d = (string) $x;    // OK - explicit cast
$e = "value: $x";    // OK - interpolation with surrounding text
$f = $x . $y;        // OK - real concatenation of two operands

Remediation

Replace the idiom with an explicit cast, (string) $x, or with strval($x) when a callable is needed. Keep concatenation and interpolation for cases that actually combine the value with other text.

References