?: 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 (removed 8.0)|| 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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