php thinks I am trying to call file() when calling variable code reference

[Jeff <jekillen@xxxxxxxxxxx>]

Hello;
These messy situations pop up occasionally and I generally try to solve it before posting
(sometimes I solve it while I am composing the post).

I have developed a system for sampling the status of variables while async request processing
is in progress. I am using it to test a search function in development. It is a function that writes
variable values to a separate file that can be viewed to analyze progress.

I am learning that problems with arguments can cause the “function name must be a string” error;

I have hit a strange problem:
php seems to think that I am trying to call file() when it sees a code reference variable:

Any thoughts?
Thank you for time and attention;
Jeff K

Warning: 
file() expects parameter 1 to be a valid path, array given in path/fSearchName.php on line 42

code generating error: (fSearchName.php)
$_code = function($_a, $_b, $_type, $_samp)
         {
          /*
           $_a: string; $_item['name'], basename($_src) w/o suffix
           $_b: string; search term
           $_type: string; 'dir'/'file'
           return: ['found'] = true || ['bypass'] = true;
          */
          // test code:
                $_tst = array($_a, $_b, $_type);//
                //foreach($_out as $_ind=>$_val)
                     //{
                      //$_tst[count($_tst)] = $_ind.": ".$_val;
                    // }
                $_it = $_samp($_tst, true, 'testOut.txt’);    //<<<< line 42 in error message
             //
           //.... etc.... attempts to find $_b in $_a in different circumstances
          }
          
code that $_samp is a reference to:
$_code = function($_vars, $_swich, $_target)
               {
                /*
                 $_vars: array; variables to be sampled
                 $_swich: boolean; true/false, true to write sample, false to clear sample file
                 $_target: string; path/file to sample file.
                */
                if($_swich === true && count($_vars) > 0)
                  { 
                   $_sample = '';
                   $_sampleArray = [];
                   for($_itr= 0; $_itr < count($_vars); $_itr++)
                     {
                      $_sampleArray[count($_sampleArray)] = $_vars[$_itr];
                     }
                   $_sample = implode( $_sampleArray, "\n");
                   @$_FO = fopen($_target, 'a');
                   if(!$_FO)
                     {
                      return false;
                     }
                   fwrite($_FO, $_sample."\n");
                   fclose($_FO);
                   return true;
                  }
                else if($_swich === false)
                  {
                   @$_FO = fopen($_target, 'w');
                   if(!$_FO)
                     {
                      return false;
                     }
                   fwrite($_FO, '');
                   fclose($_FO);
                   return true;
                  }
                return "error:arguments";
               }