Using preg_replace_callback to find and replace a function signature with a variable number of parameters

Using the PHP preg_replace_callback function, I want to replace the occurrences of the pattern “function([x1,x2])” with substring “X1X2”, “function([x1,x2,x3])” with substring “X1X2X3”, and in general: “function([x1,x2,…,x2])” with substring “X1X2…Xn” — in a given string.

Thanks to Wiktor in this previous question, I have it working for functions that take two arguments:

// $string is the string to be searched
$string = preg_replace_callback('/function([([^][s,]+),([^][s,]+)])/', function ($word) {
        $result = strtoupper($word[2]) . strtoupper($word[2]);              
        return $result;
        }, $string);

I want to move one step further and make it work for functions with an arbitrary number of arguments. I tried using the regex '/function([[([^][s,]+)]+[,]*])/' as a way of saying I want a repeated non-white substring followed optionally by a comma — to account for the last function argument that is not followed by a comma. This however made PHP moan about the regex not being correct.

Any help is appreciated,

Thanks.

Answer

You can match and capture all contents between function([ and ]) with a simple binary_function([(.*?)]) regex and then split the contents with a comma, and join back the uppercased strings:

$text = 'binary_function([x,y]) and binary_function([x1,y1,z1])';
echo preg_replace_callback('~binary_function([(.*?)])~', function ($m) {
    return implode("", array_map(function ($x) { return strtoupper($x); }, explode(",", $m[1])));
}, $text);
// => XY and X1Y1Z1

See the PHP demo.

You may trim() the input values if there can be spaces inside the ([ and ]).