?: Elvis OperatorReturns the right operand if the left operand is falsy (expression)
The Elvis Operator is a little like a conditional where the result of the operation is the first non-falsy value from left to right.
A falsy value is any of the following:
null data typestr or generic with the value false, null, 0, no, off, fail, failed, or disablednum, float or int) with the value 0false» $foo = $bar ?: "baz"If $bar is falsy, then the value of $foo will be “baz”.
» $unset_variable ?: null ?: false ?: "foobar"
foobarWikipedia explains this best where it says:
The name “Elvis operator” refers to the fact that when its common notation,
?:, is viewed sideways, it resembles an emoticon of Elvis Presley with his signature hairstyle.
err): Print a line to the stderrexpr): Expressions: mathematical, string comparisons, logical operatorsout): Print a string to the stdout with a trailing new line charactertrypipe): Checks for non-zero exits of each function in a pipelinetry): Handles non-zero exits inside a block of code&& And Logical Operator: Continues next operation if previous operation passes?? Null Coalescing Operator: Returns the right operand if the left operand is empty / undefined (expression)? stderr Pipe: Pipes stderr from the left hand command to stdin of the right hand command (DEPRECATED)|| Or Logical Operator: Continues next operation only if previous operation failsThis document was generated from gen/expr/elvis-op_doc.yaml.
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