Why Does This PHP Array Interpolation Syntax Work?

Interpolation of Associative Arrays in PHP: A Syntax Anomaly

When dealing with PHP's string-indexed arrays, the interpolation of their elements can exhibit unexpected behavior. Specifically, while it is common to use the syntax {$ha['key1']} or {$ha[key1]} to interpolate array elements, the less intuitive forms $ha['key1'] and $ha[key1] also appear to work. However, the latter two methods issue warnings.

Curiously, the syntax $ha[key1] produces correct output without any warnings. This seemingly inconsistent behavior raises the question: why does this specific interpolation method work, and can it be relied upon?

Understanding the Syntax

The documentation for PHP variable interpolation covers all of the available methods. It is evident that the syntax $ha['key1'] and $ha[key1] are not officially supported for interpolation. However, the reason behind this exception is unclear.

Reliance and Consistency

Despite its unorthodox nature, the $ha[key1] interpolation method does produce correct output. However, there is no guarantee that this behavior will remain consistent in future versions of PHP. It is possible that this anomaly will be patched in a later release, leading to unexpected errors if your code relies on this method.

Hence, it is advisable to stick with the standard syntax {$ha['key1']} or {$ha[key1]} to avoid any potential inconsistencies or unpredictable outcomes.

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