arrays - PHP: implode() Invalid arguments passed -

i using codeigniter , validation rules - custom callback validation. anyway, seems not ci related think.

i've got function return string …

function array_implode($a) {   return implode(',', $a); } 

… message implode(): invalid arguments passed

but var_dump() shows me this:

array(2) {   [0]=> string(10) "first item"   [1]=> string(11) "second item" } 

what wrong?

why? why write function, calls std function? why not write implode(',', $array); instead of adding overhead of function call?

also: var_dump puts out array? dump of $a inside array_implode function? sure $a going array, , insist on keeping array_implode function, edit code this:

function array_implode(array $a) {//type hinting: function work if $a array     return implode(',',$a); }