PHP: default function parameter value for a lambda

Question

Is it possible for a PHP function which has a lambda parameter to have a default value?

While the following works fine:

function calcValue($func) {
  echo $func(5);
}

calcValue(function($a){return 2*$a;});

when I try:

function calcValue($func = function($a){return 2*$a;}) {
  echo $func(5);
}

I get a parse error:

Parse error: syntax error, unexpected 'function' (T_FUNCTION)

Community · Accepted Answer · 2017-05-23 10:32:16Z

1

A default value must be a constant expression. See this question for more details: PHP Anonymous Function as Default Argument?

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answered Dec 2, 2013 at 18:43

user2816674

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Comments

Marc B · Accepted Answer · 2013-12-02 18:43:43Z

1

Default values in function calls have to be constants. They cannot be a dynamic value/expression result.

good: function($foo = 'bar');
bad:  function($foo = bar());
bad:  function($foo = 'ba' . 'r'); // to PHP it's still an expression.

answered Dec 2, 2013 at 18:43

Marc B

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PHP 5.6 will support constant scalar expression (3rd variant) - see wiki.php.net/rfc/const_scalar_exprs