<?php
error_reporting(-1);
$String = 'isNumeric(right(trim ( ,contract_id,),-1, j( ) ,"  ", bob, george(five(four, two))))';

$func      = '\w+';
$const     = '[\w*&^+-]+';
$wspconst  = '[\w*&^+\s-]+';

$GetRx = '\s*((?:\s*('.$func.')\s*[(](?:(?>(?:(?!\s*'.$func.'\s*[(]|[)]).)+)|(?1))*[)]))';
$ParseRx = '((?:\s*('.$func.')\s*[(]((?:(?>(?:(?!\s*'.$func.'\s*[(]|[)]).)+)|(?1))*)[)]|\s*["\']('.$wspconst.')["\']\s*|\s*('.$const.')\s*|(?<=,)|(?<=^)(?!\s*$)))';

preg_match_all('/'.$GetRx.'/', $String, $Results, PREG_SET_ORDER);

foreach($Results as $Res){
    $FinalRes = parse_func($Res[1]);
    break;
}

if(isset($FinalRes)){
    print_r(json_decode($FinalRes));
}


function parse_func($String=''){
    GLOBAL $ParseRx;

    if($String == ''){
        return '';
    }

    $String = preg_replace_callback('/'.$ParseRx.'/', 'parse_callback', $String);
    return $String;
}

function parse_callback($Matches){
    $fName = (isset($Matches[2]) ? $Matches[2] : '');
    $fBody = (isset($Matches[3]) ? $Matches[3] : '');
    $fConst = (isset($Matches[4]) ? $Matches[4] : '').(isset($Matches[5]) ? $Matches[5] : '');

    if($fBody != ''){
        return '{"'.$fName.'": ['.(parse_func($fBody)).']}';
    }

    return '"'.$fConst.'"';
}
?>