Question

Quick one for you guys.

Say I have a function that outputs a string:

function myString()
{
      echo 'Hello World';
}

How would I go about testing to see if the function outputs any data?

if(myString() ==''){ 
      echo ''Empty function;  
}

Answer 1

Using output buffer functions:

function testFunctionOutput($f, $p = array()){
    ob_start();
    call_user_func_array($f, $p);
    $s = ob_get_contents();
    ob_end_flush();
    return (bool)($s !== '');
}

So say…

function testa(){
  echo 'test';
}

function testb($b){
  $i = 20 * $b;
  return $i;
}

var_dump(testFunctionOutput('testa'));
var_dump(testFunctionOutput('testb', array(10)));

Alternative version suggested by Felix:

function testFunctionOutput2($f, $p = array()){
    ob_start();
    call_user_func_array($f, $p);
    $l = ob_get_length();
    ob_end_clean();
    return (bool)($l > 0);
}