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POParentheses altering semantics of function call result
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  1. POParentheses altering semantics of function call result
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    copied!<p>It was noted in <a href="https://stackoverflow.com/questions/6726219/strict-standards-error">another question</a> that wrapping the result of a PHP function call in parentheses can somehow convert the result into a fully-fledged expression, such that the following works:</p> <pre><code>&lt;?php error_reporting(E_ALL | E_STRICT); function get_array() { return array(); } function foo() { // return reset(get_array()); // ^ error: "Only variables should be passed by reference" return reset((get_array())); // ^ OK } foo(); </code></pre> <p>I'm trying to find anything in the documentation to <strong>explicitly</strong> and unambiguously explain what is happening here. Unlike in C++, I don't know enough about the PHP grammar and its treatment of statements/expressions to derive it myself.</p> <p>Is there anything hidden in the documentation regarding this behaviour? If not, can somebody else explain it without resorting to supposition?</p> <hr> <h3>Update</h3> <p>I first found <a href="http://www.icosaedro.it/articoli/php-syntax-ebnf.txt" rel="nofollow noreferrer">this EBNF</a> purporting to represent the PHP grammar, and tried to decode my scripts myself, but eventually gave up.</p> <p>Then, <a href="https://stackoverflow.com/questions/3609110/standalone-grammar-and-parser-for-php/3786034#3786034">using <code>phc</code></a> to generate a <code>.dot</code> file of the two <code>foo()</code> variants, I <a href="https://stackoverflow.com/questions/1494492/graphviz-how-to-go-from-dot-to-a-graph">produced</a> AST images for both scripts using the following commands:</p> <pre><code>$ yum install phc graphviz $ phc --dump-ast-dot test1.php &gt; test1.dot $ dot -Tpng test1.dot &gt; test1.png $ phc --dump-ast-dot test2.php &gt; test2.dot $ dot -Tpng test2.dot &gt; test2.png </code></pre> <p>In both cases the result was exactly the same:</p> <p><a href="https://i.stack.imgur.com/XWZMx.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/XWZMx.png" alt="Parse tree of snippets 1 and 2"></a></p>
 

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