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run code in 200+ php & hhvm versions
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<?php $great = 'abc'; ${'great '} = 'def'; const great = 'ghi'; $ghi = '...'; ${"ෝ"} = 'Meh'; // ${\u{ddd}} = 'Meh'; var_dump("${great }"); // outputs the constant value's variable value var_dump("${'great '}"); // outputs the ${'great '} variable value var_dump("${great}"); // outputs the $great variable value var_dump("${'ෝ'}"); // outputs the ${\u{ddd}} variable value var_dump("${ෝ}"); // outputs the ${\u{ddd}} variable value /* Even though "great " is not a valid variable name, neither is "\u{ddd}" but that still works. I'd therefore expect "${great }" to firstly search for a variable named "great " before falling back to evaluating the expression first. */
Output for 5.5.0 - 7.3.0rc3
string(3) "..." string(3) "def" string(3) "abc" string(3) "Meh" string(3) "Meh"